I've come up with the same. Digging through some logs and stuff, here is what is setting it off:

Debug Information Level=0
BackupRegKey[HKEY_CLASSES_ROOT\ChatFile\DefaultIcon]
BackupRegKey[HKEY_CLASSES_ROOT\ChatFile]
BackupRegKey[HKEY_CLASSES_ROOT\ChatFile\Shell]
BackupRegKey[HKEY_CLASSES_ROOT\ChatFile\Shell\open]
BackupRegKey[HKEY_CLASSES_ROOT\ChatFile\Shell\open\command]
BackupRegKey[HKEY_CLASSES_ROOT\ChatFile\Shell\open\ddeexec]
BackupRegKey[HKEY_CLASSES_ROOT\ChatFile\Shell\open\ddeexec\Application]
BackupRegKey[HKEY_CLASSES_ROOT\ChatFile\Shell\open\ddeexec\ifexec]
BackupRegKey[HKEY_CLASSES_ROOT\ChatFile\Shell\open\ddeexec\Topic]
BackupRegKey[HKEY_CLASSES_ROOT\.cha]
BackupRegKey[HKEY_CLASSES_ROOT\.chat]

and

Damage Cleanup Engine (DCE) 3.5(Build 1119)
Windows XP(Build 2600: Service Pack 1)

Start time : Fri Mar 26 02:49:08 2004


Load Damage Cleanup Template (DCT) "H:\WINDOWS\tsc.ptn" (version 298) [success]
BKDR_IRCFLOOD.X[virus found]
-->delete registry data("HKEY_CLASSES_ROOT","ChatFile\DefaultIcon",""E:\mIRC\mirc.exe"") success
-->delete registry key("HKEY_CLASSES_ROOT","ChatFile","") success
-->delete registry key("HKEY_CLASSES_ROOT",".cha","") success
-->delete registry key("HKEY_CLASSES_ROOT",".chat","") success

Complete time : Fri Mar 26 02:49:14 2004

Execute pattern count(718), Virus found count(1), Virus clean count(1), Clean failed count(0)