I recently upgraded my graphics card to MIS N570GTX with 1280Mb of VRAM and I'm having a strange problem with FPS drop in Skyrim. When I first start Skyrim my FPS is at 60 and then as I watch it gradually drops to 50 then 40 then 30 and then eventually goes below 20. It then varies up and down a bit, but generally stays <30 and goes below 20 all the time. This happens if I just stand in one place outside, I don't need to move my character around to see this.
I'm using MSI Afterburner to monitor the card and its temperature never goes above 60C and memory usage is typically well below 1280 (usually well below 800Mb). This happens on High or Ultra (doesn't see to make a difference). If I go to Medium the frame rate still drops but not as far (maybe to the 20-30 range). I removed all of my graphics mods and even removed the Bethesda HD pack. I'm using the latest released Nvidia driver (295).

Any idea what may be causing this? Are there any setting I can change? Do I have a defective graphics card?

Bump. Anyone encounter a similar problem?

Knowing about your system would help...

could be running out of System ram..how much you have?
Could be a CPU bottle neck...what CPU you have and what speed your running...
Could be running a 32 bit OS...
With the Upgraded GPU did you also get a proper power supply?

Try rolling back to the 290 Skyrim edition Nvidia driver.

all anyone can do is Guess...heres mine....

Shadows on Ultra?? Try High, ..shadows in Skyrim can be a FPS killer. so can AO and using the AA/AF from the Launcher.

Turn down shadows.

Thanks for your responses. Here's an update. I tried everything I could: disabled AA and AO, ran at Medium, reverted back to 280 driver, ran in a window. Nothing helped - after running for a few minutes the rate drops down to 20fps and lower ( a bit higher in Medium). It always starts at 60fps, so it shouldn't be related to capabilities of the GPU or processor. BTW I'm running 64bit Win7 on Intel Quad core ( sorry don't remember clock speed), and my power supply is 1000W.

I finally went back to my old card (GeForce 9800 with 512Mb RAM) and the frame rate is now stable at ~30-34fps with settings on High (no HD pack). So I concluded that my new card was defective and am returning it.
I ordered a EVGA 570 with 2Gb ram instead. Will see if I have better luck with it.

I am willing to bet your correct that its defective and that EVGA with the double VRAM is going to be way better for Skyrim especially if you want to add some graphics mods. Smart move.