Please see - [dwr-users] Re: DWR 2.0.7 Download Wrong? from the users mailing list.
BTW: It would be nice if you allowed JIRA wiki format to be used in comments, so that I could mark up these comments better
Sean, we cannot use ConcurrentHashMap for the 2.x branch (compatible with pre-1.5).
If you look in trunk you will notice I am using ConcurrentHashMap.
Ah, excellent... you are way ahead of me.
I just enabled the wiki renderer for comments.