So yeah, every time I click to swing my weapon, punch, shoot an arrow, or cast a spell, the game locks up, and can't be closed without a Ctrl+Alt+Del. So I tried starting a new game. That worked--I was able to punch without the game freezing. This leads me to believe it has something to do with my save file. So, if nothing else works, I have there's that option of starting a new game. Obviously, however, I'm hoping it doesn't come to that--I've worked awful hard to get where I am now.

I read http://uesp.net/wiki/Oblivion:Technical_Support that I should use http://nightmare2013.brashendeavors.net/ So I did. I made a backup like it told me to, then ran the reset utility. It asked me whether I was using SP1 or SP2, but I'm using SP3, so I selected SP2. It didn't work--not only did it still freeze on attack, but also the music stopped working. So I restored the backup and tried it again, this time with SP1. That didn't work either--it made Oblivion crash once I tried to load my game. I restored the backup again, and it stopped crashing, but the freezing is still there.

Does anyone have any clue how the hell I can fix this?

Running any mods? Deadly Reflex 5 has been known to cause this for some people.

Yep, that was the problem. I disabled Deadly Reflex, and now it works. Thanks.

It's a shame, though. I really like DR--it makes the combat so much more intuitive. Anyone by chance know how to fix this? It'd be a bummer if I have to go back to Bethesda's boring vanilla combat.

Yes, there is a fix for it. I'll go dig up the link.

Edit: Turns out it's now available directly from the http://www.tesnexus.com/downloads/file.php?id=8273. It's the hotfix at the very bottom under the Files header.