Looks like in 1.6 there is a new public "SimpleEntry" class in AbstractMap. I wrote my own "SimpleEntry" for MapCopy, since 1.5 did not have this exposed. It seems there might be a compatibility issue if JBoss Cache was compiled for 1.6 and later run on 1.5. I assume this is not the case, and instead there's some sort of Java bug. How was your Cache 2.0 built? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4044563#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...