Are you using Spybot or any other type of spyware detection utility? Sounds like some kind of malware might have hijacked your browser.
I use IE for one thing only... to access the Merriam Webster online dictionary. It ports the pronunciation sound directly to my sound card. Mozilla either can't do that or I haven't configured it to do that. For some odd reason Mozilla has to launch Media Player to play the sound, which adds 10-15 seconds to the process. In fact, I don't actually launch IE to do that, I just open a single window, in Windows Explorer, and I'm done in 3 seconds.
All in all, I'm a big Mozilla fan though.