Copied and pasted from the wiki.

Game freezes after click to swing a weapon, shoot off an arrow, or use a spell

Problem
The game freezes after swinging a weapon or more likely shooting off a bow or spell, must require reboot or if luckier, use task manger to forcefully close Oblivion.
Cause
DirectShow filters (codecs) conflict with oblivion
Solution
Use Nightmare2013's CODEC Reset Utility v4.1, which is available on his/her website here.

I tried using Nightmare2013's CODEC Reset Utility v3.0, but it was made back in '06 so I believe it's incompatible from my attempts of using it.

I made a post last week or so of this same problem, and someone snark-fully assumed it was from me not having a load order, and that there are
other ongoing problems with my game that I've yet to realize... WRONG! I've had no problems without OBMM, up to this point. And now with it,
no new problems, but the same one persists. This is the smoking gun :flamethrower: xD. So if anybody can help me fix this I'd appreciate it greatly

Are you using an older Deadly Reflex? The symptoms are the same...

Thank you for the speedy reply! I am using Deadly Reflex 5. I'm not sure how old that is. However when I've disabled it and tried again, it still freezes the game :S. (just for the 3 mentioned animations) Luckily I don't have to hard-boot as the wiki mentioned some do...

Edit: Actually I lied, I just tried disabling Deadly Reflex again and for the first time in forever it didn't crash! Is there any way I can make Deadly Reflex work? I must have forgot to disable one of the 3 esp's last time

There is a hot fix for Deadly Reflex. Try looking in the Relz thread or on Nexus.