Index: activemq-core/src/main/java/org/apache/activemq/openwire/OpenWireFormat.java
===================================================================
--- activemq-core/src/main/java/org/apache/activemq/openwire/OpenWireFormat.java	(revision 472254)
+++ activemq-core/src/main/java/org/apache/activemq/openwire/OpenWireFormat.java	(working copy)
@@ -148,25 +148,28 @@
                     BooleanStream bs = new BooleanStream();
                     size += dsm.tightMarshal1(this, c, bs);
                     size += bs.marshalledSize();
-    
-                    bytesOut.restart(size);
-                    if( !sizePrefixDisabled ) {
-                        bytesOut.writeInt(size);
+
+                    synchronized (bytesOut) {
+                        bytesOut.restart(size);
+                        if( !sizePrefixDisabled ) {
+                            bytesOut.writeInt(size);
+                        }
+                        bytesOut.writeByte(type);
+                        bs.marshal(bytesOut);
+                        dsm.tightMarshal2(this, c, bytesOut, bs);
+                        sequence = bytesOut.toByteSequence();
                     }
-                    bytesOut.writeByte(type);
-                    bs.marshal(bytesOut);
-                    dsm.tightMarshal2(this, c, bytesOut, bs);                
-                    sequence = bytesOut.toByteSequence();
-                    
                 } else {
-                    bytesOut.restart();
-                    if( !sizePrefixDisabled ) {
-                        bytesOut.writeInt(0); // we don't know the final size yet but write this here for now.
+                    synchronized (bytesOut) {
+                        bytesOut.restart();
+                        if( !sizePrefixDisabled ) {
+                            bytesOut.writeInt(0); // we don't know the final size yet but write this here for now.
+                        }
+                        bytesOut.writeByte(type);
+                        dsm.looseMarshal(this, c, bytesOut);
+                        sequence = bytesOut.toByteSequence();
                     }
-                    bytesOut.writeByte(type);
-                    dsm.looseMarshal(this, c, bytesOut);                
-                    sequence = bytesOut.toByteSequence();
-                    
+
                     if( !sizePrefixDisabled ) {
                         size = sequence.getLength()-4;
                         int pos = sequence.offset;
@@ -177,10 +180,12 @@
                 
                 
             } else {
-                bytesOut.restart(5);
-                bytesOut.writeInt(size);
-                bytesOut.writeByte(NULL_TYPE);
-                sequence = bytesOut.toByteSequence();
+                synchronized (bytesOut) {
+                    bytesOut.restart(5);
+                    bytesOut.writeInt(size);
+                    bytesOut.writeByte(NULL_TYPE);
+                    sequence = bytesOut.toByteSequence();
+                }
             }
             
             if( ma!=null ) {
@@ -240,19 +245,23 @@
             	DataOutput looseOut = dataOut;
             	            	
             	if( !sizePrefixDisabled ) {
-	                bytesOut.restart();
-	                looseOut = bytesOut;
-                }
-                
-                looseOut.writeByte(type);
-                dsm.looseMarshal(this, c, looseOut);
-                
-                if( !sizePrefixDisabled ) {
-                    ByteSequence sequence = bytesOut.toByteSequence();
+                    ByteSequence sequence = null;
+                    synchronized (bytesOut) {
+                        bytesOut.restart();
+                        looseOut = bytesOut;
+
+                        looseOut.writeByte(type);
+                        dsm.looseMarshal(this, c, looseOut);
+
+                        sequence = bytesOut.toByteSequence();
+                    }
+
                     dataOut.writeInt(sequence.getLength());
                     dataOut.write(sequence.getData(), sequence.getOffset(), sequence.getLength());
+                } else {
+                    looseOut.writeByte(type);
+                    dsm.looseMarshal(this, c, looseOut);
                 }
-
             }
             
         } else {