I use OBSE, but even without OBSE the problem is the same.
When I first click on oblivion.exe, the game will not load. If I look in my task manager, it shows that oblivion and its linked rundll file are in the processes list, but the game just isn't loading. BUT, then if I open obvlivion.exe again, then it will load, but I'll end up with two oblivion processes running at the same time.

After clicking it the first time, I can go into my task manager and "end process" for oblivion.exe. Then, when I try opening oblivion again, it will work. BUT, if I "end process tree" instead, then Oblivion won't work unless I try opening it two times again.

I think this may be causing occasional crashes. I'm using a lot of mods, but I didn't start having this problem until after having played for a long time. I haven't added any new mods in about a year.

Any ideas?