mIRC reported as IRC.Zapchast

[AdamM]

After upgrading to 1.6.2, when I went to use my copy of mIRC 6.0.3 for the first time the Resident killed it and told me I had in fact executed IRC.Zapchast, a backdoor trojan. This is a legitimate (albeit old) copy of mIRC that I've had on my system and used since February 2008. TeaTimer is 1.6.6.32. My OS is XP Professional. Resident logs this:

29/03/2009 13:37:42 Encountered and terminated IRC.Zapchast in C:\Program Files\mIRC\mirc.exe!