Hey, umm, yeah I got the same problem.
My computer was literally crawling with viruses, I think avast found about 20 of them, I dont have the names, but I do know I had sasser and a few variations of MSblaster.
Anyway, Internet Explorer, Windows Media Player, Windows File Search, and Kazaa Lite K++ arent working (avast and the virus cleaner work fine). The standard XP Error Report box comes up and under tech information it mentions ahascr.dll in all of them except for the file search, which just shuts down explorer, but I'm, pretty sure thats related.
I just did a full system scan 2 days ago and used the virus cleaner yesterday, so I really dont know whats up. I checked dll-files.com for ahascr.dll and it found nothing, asked a few of my freinds to search their system for it, and they didnt find anything. I'll probably end up scanning the system again for viruses. Its just weird, I searched google for ahascr.dll and all that came up was this topic :/ If this was caused by a virus wouldnt there be more mention of it?