Whooooaa Nelly! If this ain't a deal-breaker, I dunno what is. I personally use Trillian, & now that I know this little tidbit of info, IE7 certainly won't be making its way onto my b0xen until this flaw is fixed....

"Some Internet Explorer 7 testers who loaded the Beta 1 bits onto their systems have found a nasty surprise BetaNews has learned: their instant messaging software crashes. Trillian, a popular multi-network IM client, Gaim and IM2 all spit out error messages when loaded alongside IE7, and the only fix is to uninstall Microsoft's new browser."