I have the problem. When I started the mission, Sam Fischer drops in the water and mission is "assignment failed".
my computer config:
pentium 4 3ghz
1 gigaram
directx 9.0c.(november 2007)
nvidia geforce 7300 gt (93.83 drivers number)
Why this happend?!?!

Because SCDA is really buggy.

Tru updating your graphics card drivers, I think they are rather old.

i fix this bug
1.set resolution 800-600 or 1024-768
2. only turn off high detail shader
3. play and enjoy

I tried freed2006's suggestion and it works. Thanks, freed.

What buggy, buggy game. The only reason I persevered through this abomination is because the story was really good.