If the initial claim was that there's a Win7 compatibility issue you could try running in compatibility mode for XP or Vista (right click mirc.exe, go to Properties -> Compatibility). If it still freezes there, it could be something with your hardware/drivers/AV that doesn't like mIRC + Win7, but it wouldn't *just* be mIRC.

- argv[0] on EFnet #mIRC
- "Life is a pointer to an integer without a cast"