About the saved game issues, it isn't due to save games : even if you start a new game, it happens sometimes, I can't manage to reproduce it every time I play the game (although it seems to happen more in complex maps, i'm not sure, it's really random).
I'll try to reduce my GFX details, but it's a shame i have to do so while it runs fine on Windows.
EDIT : actually I never reproduce it with Shaders set to Low, but with UltraHigh (and maybe High, MEdium etc) it sometimes occurs.
Once, I even got the water to be green, really weird !
EDIT2 : i just reproduced it, the problem aren't the shaders, it happens everytime i set VFX to at least Medium... and console says "03/04/09 20:09:42 kernel NVDA(OpenGL): Channel exception! status = 0xffff info32 = 0xd = GR: SW Notify Error"... Anyway if I set VFX to medium and move my mouse a lot (to see the whole map) in big missions like the Mount Fuji mission (soviet campaign), the game starts to lag a lot (like 1fps) and when I "look" at the water, it's 30fps again... But if I set VFX to Very Low, i'm safe, didn't try Low yet... And no, my GPU works fine, it's the only game that does this, other games ,even other Cider games don't do this.
EDIT3 : just tried with VFX set to Low and everything else in UltraHIgh (max details) and the bug is gone... But the game looks a lot nicer with VFX to medium (i miss bloom !)... Why do I have this bug ?
EDIT 4 : Just tried to set VFX to max but Shadows to Low now : the game is perfectly smooth and nice (i'd rather have all VFX than shadows)... So I guess you are right the problem is VRAM related and not specific to some effects. Isn't this fixable, I mean on Windows, 512MB of VRAM is enough for RA3 ! The same happens in fullscreen or windowed btw