For the Jamba part (I don't use ISBoxer):

Check that the communication channels are the same for all toons. /jamba -> Core: Communications tab. Esp. check the toon with the problem.

If the channel name and password is the same, then try clearing out the chat channel files for the offending toon.

http://www.fukt.bsnet.se/~k/wow/stuf..._settings.html

See this thread for more info:

http://www.dual-boxing.com/showthread.php?t=29048