STUPID WINDOOZZZZ!

Right, had to get it out.

Wasted two and a half hours this morning trying to figure out why my Oblivion wouldn't start. Of course I was blaming the mods, OBSE, everything... Ticking them off one by one, removing plugins until I was left with NAKED Oblivion - and it still wouldn't start! That is, it starts, plays the Bethesda logos video, and then just hangs there. Or occasionally it manages to progress to the main menu and then hangs when you try to load a save - or even start a new game!
But when the naked Oblivion did the same, I finally had to concede that it had NOTHING to do with mods...

Should have thought of that earlier... Like two and a half hours earlier!
A reboot fixed the problem.
There was no Windows update between yesterday and today, but I do have a suspect. I played Two Worlds II yesterday before bed, and that game has its own video handling built in - it was made before the standard DirectX or whatever came out. It did take a long time to start up yesterday, and the screen flickered a few times - I think the video card was changing some settings, and that must have confused Oblivion. But now I can run either game without issues. <giant sigh of relief>