Glad to hear that resolved your issue. The KB921337 hotfix worked fine for me, however I assumed that as you were using Windows XP SP2, you were not updating your version of XP with all subsequent patches, which would normally take it to SP3 :-)
It was a tricky issue to track down as I had to slowly integrate changes from 7.27 in 7.25 and recompile after each change to pin it down. I was pretty sure it was not a non-supported function issue as, usually, if an application uses a non-supported function, Windows will display an error dialog the moment you try to run that application.
I try to make sure mIRC uses functions that are available across all supported versions of Windows. If a function is only supported in a newer version of Windows and I need to use it to support a new Windows-specific feature, mIRC uses dynamic loading to ensure it continues to work on older versions of Windows.
