Gamma level won't save (bought on steam)

[strobeshow]

yes, i changed the one in my documents. when launching the game, it says it's on the level i manually changed it to, but it's really not. so it says it's on 1.3, but it's still the same as 1.0

running as an admin doesn't help, just tried it.

im on windows 7 64bit, forgot to say, sorry. i should also say i have a gtx 275 (nvidia).
just updated to the latest driver to make sure that wasnt the issue. still have the issue however, so that's ruled out.