I usually have Framerate around 40fps with all settings maxed out and few other mods including Skyrim HD high texture mod
and Realistic Lightning and Skyboost in latest versions installed through Nexus mod manager.

Im playing with 1900x1200 resolution on medium-class rig.
My rig:
Intel Quad Q9550 -2.98Mhz
4gb ram GoodRam (around 800mhz)
Geforce 560gtx (latest beta drivers 290.53)

Yesterday i have some problems with stuttering from time to time when i enter interior then leave outside.

It looks like i have 40fps then enter some interior then go outside after few minutes and i have around 10 fps.

I think that may be something with latest patch becouse on previous version of Skyrim problem doesn't occur.
It may be something with cleaning cells, kind of standard problem of Gamebryo engine (still present in Skyrim under another name and
sligthly modified).

When i made ALT + TAB then back to game problem with FPS goes away and i have again 40 fps.

I have no problems in other games .

Anybody could help me?
Thanks

using any program for the GPU? As I installed "gamer osd" (don't really remember exactly) from Asus it almost completely removed all my FPS drops.

Nope, but i played now and all that stutter just gone after upgrading Skyboost to version R4
and using BOSS program for Skyrim ( you can grab them from Skyrim Nexus website).
I can't explain what that was but now it seems to be okay. Anyway thank You Sweets58.

I've been noticing this too, since recently letting steam upgrade me from 1.1 to 1.3. I first tried dl'ing tesval, and then later skyboost (r3), but neither of those helped, updating graphics drivers to the 290 beta didn't help either (though a remarkable improvement in overall frames). I just played for a few hours prior to posting here; while running fraps for fps display, and hwwmonitor to check if maybe i was over heating, but my cpu temps are fine, and the gpu temps actually improved since doing the driver update (before i was seeing 85° F, now max of 72).

Alt tabbing seems to fix it just fine though, so at least there's that. I will look into BOSS and skyboost r4.

Just posting to let everyone know it's not a one-off, but from what i've seen it seems to happen most often after a laoding screen (indoors-outdoors, cities, and fast travelling)

Specs:

AMD 965 @ 4.0ghz
Crosshair V
GTX 570
8 GB G.skill cl7
WD Caviar Black

Also put your shadows in Skyrim options to : High not on Ultra. (everything else i have maxed out)

Then install latest SKYBOOST r4 - FPU version

then install and run BOSS (very easy have no fear).

Other way may be to turn off Ambient Occlusion in Nvdia drivers panel.

It helps me i played for few hours and stutters goes to hell.

Lol, BOSS screwed up the game, main menu wouldnt load, had to drop sorting mod to the bottom.

Got skyboost r4 installed, still happening though.

I have ambient occlusion activated in nvidia inspector. Does the 290 beta activate it by default?

Anyway, i'll check it out your suggestions later, i only noticed this because i had to alt tab lol