This has been
brought up in the Bug Report forums already (although Quention Center is probably a better place for it - consider it is not a Trukz bug).
The basic summery is that there are some problems that Mibbit & Coldfront need to resolve. Until then you should use a standalone client or possibly the
Coldfront PJIRC applet if you don't want to or cant install anything. Hopefully they will sort out the problems soon, I personally use a standalone client but my heart goes out to anyone who has to use clunky bloated Java applets :P