Screenshots bug

[Marmaduke]

I apologize if the question is already answered some place, I did not find it in the archives.
I have tried to take screenshots of the game but, for whatever reason, when I press the PrntScreen key, it takes a screenshot of the desktop. Effectively, I am barred from taking pictures of the game.
I use Microsoft Vista.
Does anybody have any information about this issue? My copy is legit so it is not related to some kind of software protection.

[Sombre]

Tried alt prntscrn, ctrl prntscrn, shift printscrn?

[Burnsaber]

I actually have problems too. I get a "screenshot", but it's all black.

[Marmaduke]

Tried alt prntscrn, ctrl prntscrn, shift printscrn?

I had not, and Alt-PrntScrn does indeed provide me with a lovely screenshot. Thanks to you!

(Ctrl-PrntScrn did the black screenshot thing.)