Two suggestions, Mr. V:
1. Have you tried the No Popup Chat option? It turns out that the regular chat can't handle some usernames with punctuation in them. "Mr
. Venomous" could very well be one of them.
2. Does anything in these threads look relevant to your situation?
http://forums.psychcentral.com/showthread.php?t=213354
http://forums.psychcentral.com/showthread.php?t=171843
http://forums.psychcentral.com/showthread.php?p=1754461