Sorry for the delay. Yes, it's easy to simulate but not in a deterministic way. My "brute force" test found it just bcause it launches a torrent of threads on the poor cache :) I'll see what I can do to simplify this. BTW: I am observing another exception that pops up sometimes: a ClassCastException in ReadCommittedNode.markForUpdate(), where an UnversionedNode is cast to NodeReference. This looks like a race between commit and modification to me, but I wasn't able to reproduce it in controlled environment. Any hints? View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4218553#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...