When I view the Edit Profile and Edit Options page, it looks fine. Though when I edit something and save, it gives me this error.
<vBulletin code>
I tried re-uploading the user CP files, though it still had that error.
That's vBulletin code, and you should not be posting it here. If you are using vB, then post for support on their forums.
But I'm not using vBulletin. It just gives me that code for some odd reason.
It wouldn't spawn that code for no reason. URL to your forums??
I'm not registering on your forum, can you provide test account details??
Sure...
Nick: Charizard
Pass: password
Reupload a fresh copy of usercp.php from a fresh MyBB download.
I did that just a few minutes ago. Should I do it again?
Yes. Clearly, your forum is calling random vBulletin code, which would only happen if parts of a vBulletin installation are on your site.