Map bug?

[Biggly]

I can't get the map to pop up: I've started another new game just to make sure I didn't have the 'no map' option selected, I've checked whether my tab key works (it does) and I've tried mapping the map function to another button, to no avail.

Is this some kind of meta-puzzle, am I being really stupid, or is this a bug?

[eLPuSHeR]

Are you on Steam? Try validating your game cache.

[Biggly]

Yep, Steam. Validating didn't do anything. I'll see if I can dip into the config files and have a fiddle with the settings from there.