So normally my system can run Fallout 3 at a consisten 60fps on very high settings, with maybe a few rare drops into the 40s here and there. However, I just started playing Point Lookout, and while in the swamp areas, I'm getting framerates in the 20s. After a lot of trial and error, I narrowed this down with the Full Scene Reflections setting. With that turned off, framerate goes back up to 60fps. I'm not sure why this is only a problem in Point Lookout - because of all the trees needing to be reflected I guess?

I'd really prefer not to turn it off though - I like seeing all the trees reflected in the water. Is there a tweak I can make that will allow me to have Full Scene Reflections enabled, but not have it kill performance so much? I tried setting reflection quality to low and disabling Full Detail Reflections - and that gave me 5-10fps, but that's still only enough to get me up to about 35fps in the swamps and I'd really prefer to have the framerate no lower than 45fps.

My video card is a GeForce GTX 285 and I'm on the 260.99 drivers.

You might want to try turning off HDR and use Bloom lighting instead. I was constantly crashing after a reinstall of WinXP and it seemed one of the main laggy areas was around reflecting water. I toned everything down to medium settings and kept HDR on but still got crashes. So i turned off HDR and set my settings back to max which is the same thing i did a few years ago when OBLIVION was suddenly not stable. Now after a whole day of playing i have not had one single crash with Bloom on and max settings. I do get a slight pause at times when coming across water or large puddles.

You might also want to try installing Windows Media Player 11 which made things more stable in a previous attempt but did not eliminate the crashing like turning off HDR did.

Point lookout is full of water, that's why. Even on the best setup the framerate plummets there unless you untick some of the water options