Big fps drop in skyrim

[Khaaaaaaaan]

For the past months I have been playing skyrim at Ultra (the setting it recommended for me when I first loaded up the game), and have been using using lighting replacers, high def texture packs etc. etc. I decided to start completely anew with the release of the creation kit, and so redownloaded skyrim off of steam, and put the same mods I had been using on it. When I loaded up the skyrim launcher, it tells me that now I should be using "high" settings. I turned it up to Ultra, because I had been running ultra at 60 fps, and so saw no reason why it should be different. Upon entering the game however, I had around 10 fps. I switched between windowed and nonwindowed, but it didn't make a difference. I then switched to "high" but that only gives me 20 fps. I am really confused as to why this is happening, and if there is something I can do to get my old fps back, preferably without turning my graphics settings to low.
My rig is in my signature, and I should say my graphics card is overclocked (stable) as well. Any help at all would be great, and if you need more info, just ask.

[Tankercow]

I'm gonna be that guy. Make sure your drivers are up to date and that your hardware isn't overheating.

[Khaaaaaaaan]

My drivers are updated, and as far as I can tell, there is no option to set Ambient Occlusion from the ATI control panel.

---------- Post added 2012-02-20 at 10:56 AM ----------

OK, now I am even more confused. I just unloaded all my mods, started a new game, then quit out and reloaded them all. Now I get 50 fps on ultra.... 50 is still pretty good, so I'm not going to complain, but I am very confuzzled...