diff --git a/source/de/anomic/crawler/IndexingStack.java b/source/de/anomic/crawler/IndexingStack.java
index df9c7bc05..6a491e8c9 100644
--- a/source/de/anomic/crawler/IndexingStack.java
+++ b/source/de/anomic/crawler/IndexingStack.java
@@ -78,7 +78,7 @@ public class IndexingStack {
             NaturalOrder.naturalOrder
     );
 
-    public int size() {
+    public synchronized int size() {
         return (sbQueueStack == null) ? 0 : sbQueueStack.size();
     }
 
@@ -98,33 +98,33 @@ public class IndexingStack {
     }
 
     public synchronized QueueEntry pop() throws IOException {
-    	synchronized (sbQueueStack) {
-    		int sizeBefore;
-	    	while ((sizeBefore = sbQueueStack.size()) > 0) {
-		        Row.Entry b = sbQueueStack.pot();
-		        if (b == null) {
-		        	Log.logInfo("IndexingStack", "sbQueueStack.pot() == null");
-		        	if (sbQueueStack.size() < sizeBefore) continue;
-		        	Log.logSevere("IndexingStack", "sbQueueStack does not shrink after pot() == null; trying pop()");
-		        }
-		        if (sbQueueStack.size() < sizeBefore) {
-		        	return new QueueEntry(b);
-		        } else {
-		        	Log.logSevere("IndexingStack", "sbQueueStack does not shrink after pot() != null; trying pop()");
-		        }
-		        sizeBefore = sbQueueStack.size();
-		        b = sbQueueStack.pop();
-		        if (b == null) {
-		        	Log.logInfo("IndexingStack", "sbQueueStack.pop() == null");
-		        	if (sbQueueStack.size() < sizeBefore) continue;
-		        	Log.logSevere("IndexingStack", "sbQueueStack does not shrink after pop() == null; failed");
-		        	return null;
-		        }
-		        return new QueueEntry(b);
-	    	}
-	    	Log.logInfo("IndexingStack", "sbQueueStack.size() == 0");
-	        return null;
+    	if (sbQueueStack == null) return null;
+    	// this shall not return null because it may cause a emergency reset!
+		int sizeBefore;
+    	while ((sizeBefore = sbQueueStack.size()) > 0) {
+	        Row.Entry b = sbQueueStack.pot();
+	        if (b == null) {
+	        	Log.logInfo("IndexingStack", "sbQueueStack.pot() == null");
+	        	if (sbQueueStack.size() < sizeBefore) continue;
+	        	Log.logSevere("IndexingStack", "sbQueueStack does not shrink after pot() == null; trying pop()");
+	        }
+	        if (sbQueueStack.size() < sizeBefore) {
+	        	return new QueueEntry(b);
+	        } else {
+	        	Log.logSevere("IndexingStack", "sbQueueStack does not shrink after pot() != null; trying pop()");
+	        }
+	        sizeBefore = sbQueueStack.size();
+	        b = sbQueueStack.pop();
+	        if (b == null) {
+	        	Log.logInfo("IndexingStack", "sbQueueStack.pop() == null");
+	        	if (sbQueueStack.size() < sizeBefore) continue;
+	        	Log.logSevere("IndexingStack", "sbQueueStack does not shrink after pop() == null; failed");
+	        	return null;
+	        }
+	        return new QueueEntry(b);
     	}
+    	Log.logInfo("IndexingStack", "sbQueueStack.size() == 0");
+        return null;
     }
 
     public synchronized QueueEntry remove(final String urlHash) {
diff --git a/source/de/anomic/kelondro/blob/BLOBHeap.java b/source/de/anomic/kelondro/blob/BLOBHeap.java
index bb8fc0ead..19536142c 100755
--- a/source/de/anomic/kelondro/blob/BLOBHeap.java
+++ b/source/de/anomic/kelondro/blob/BLOBHeap.java
@@ -246,7 +246,7 @@ public final class BLOBHeap extends BLOBHeapModifier implements BLOB {
     /**
      * close the BLOB table
      */
-    public synchronized void close() {
+    public synchronized void close(boolean writeIDX) {
     	if (file != null) {
             try {
                 flushBuffer();
@@ -255,7 +255,7 @@ public final class BLOBHeap extends BLOBHeapModifier implements BLOB {
             }
         }
     	this.buffer = null;
-    	super.close();
+    	super.close(writeIDX);
     	assert file == null;
     }
 
@@ -443,7 +443,7 @@ public final class BLOBHeap extends BLOBHeapModifier implements BLOB {
             heap.remove("aaaaaaaaaaab".getBytes());
             heap.remove("aaaaaaaaaaac".getBytes());
             heap.put("aaaaaaaaaaaX".getBytes(), "WXYZ".getBytes());
-            heap.close();
+            heap.close(true);
         } catch (final IOException e) {
             e.printStackTrace();
         }
diff --git a/source/de/anomic/kelondro/blob/BLOBHeapModifier.java b/source/de/anomic/kelondro/blob/BLOBHeapModifier.java
index df440512d..d21e147ae 100644
--- a/source/de/anomic/kelondro/blob/BLOBHeapModifier.java
+++ b/source/de/anomic/kelondro/blob/BLOBHeapModifier.java
@@ -105,10 +105,7 @@ public class BLOBHeapModifier extends HeapReader implements BLOB {
      */
     public synchronized void close(boolean writeIDX) {
         shrinkWithGapsAtEnd();
-        if (file != null) {
-            file.close();
-        }
-        file = null;
+        super.close(writeIDX);
         
         if (writeIDX && index != null && free != null && (index.size() > 3 || free.size() > 3)) {
             // now we can create a dump of the index and the gap information
@@ -134,9 +131,9 @@ public class BLOBHeapModifier extends HeapReader implements BLOB {
             }
         } else {
             // this is small.. just free resources, do not write index
-            free.clear();
+            if (free != null) free.clear();
             free = null;
-            index.close();
+            if (index != null) index.close();
             index = null;
         }
     }
diff --git a/source/de/anomic/kelondro/blob/HeapReader.java b/source/de/anomic/kelondro/blob/HeapReader.java
index 0b7613261..86a9bb4c1 100644
--- a/source/de/anomic/kelondro/blob/HeapReader.java
+++ b/source/de/anomic/kelondro/blob/HeapReader.java
@@ -290,7 +290,7 @@ public class HeapReader {
     /**
      * close the BLOB table
      */
-    public synchronized void close() {
+    public synchronized void close(boolean writeIDX) {
         if (file != null) file.close();
         file = null;
         heapFile = null;
diff --git a/source/de/anomic/kelondro/table/Stack.java b/source/de/anomic/kelondro/table/Stack.java
index b2e0f9524..02542f7d9 100644
--- a/source/de/anomic/kelondro/table/Stack.java
+++ b/source/de/anomic/kelondro/table/Stack.java
@@ -68,6 +68,8 @@ public final class Stack extends FullRecords {
         try {
             return new Stack(file, rowdef);
         } catch (final IOException e) {
+        	Log.logSevere("Stack", "Stack file open failed, deleting stack file " + file.toString());
+        	e.printStackTrace();
             FileUtils.deletedelete(file);
             try {
                 return new Stack(file, rowdef);
@@ -205,7 +207,7 @@ public final class Stack extends FullRecords {
         return row().newEntry(n.getValueRow());
     }
     
-    void unlinkNode(final Node n) throws IOException {
+    private void unlinkNode(final Node n) throws IOException {
         // join chaines over node
         final RecordHandle l = n.getOHHandle(left);
         final RecordHandle r = n.getOHHandle(right);
@@ -291,12 +293,6 @@ public final class Stack extends FullRecords {
         }
     }
 
-    public String hp(final RecordHandle h) {
-        if (h == null)
-            return "NULL";
-        return h.toString();
-    }
-
     public void print() throws IOException {
         super.print();
         final Iterator<Row.Entry> it = stackIterator(true);
diff --git a/source/de/anomic/plasma/plasmaSwitchboard.java b/source/de/anomic/plasma/plasmaSwitchboard.java
index 201dd66a1..e8cd367a2 100644
--- a/source/de/anomic/plasma/plasmaSwitchboard.java
+++ b/source/de/anomic/plasma/plasmaSwitchboard.java
@@ -1233,6 +1233,7 @@ public final class plasmaSwitchboard extends serverAbstractSwitch<IndexingStack.
                     ", remoteStackSize=" + crawlQueues.noticeURL.stackSize(NoticedURL.STACK_TYPE_REMOTE));
             try {
                 final int sizeBefore = crawler.queuePreStack.size();
+                if (sizeBefore == 0) return null;
                 nextentry = crawler.queuePreStack.pop();
                 if (nextentry == null) {
                     log.logWarning("deQueue: null entry on queue stack.");