Introduction and problem. (It was working, now it's not.)

[dantheengineer]

Hi, i bought and successfully installed Deus Ex. Human Revolution and have since played about 64 happy hours on it. After a few cliches, that restarting seemed to over come. It locked up after a game save. Upon restarting it asks for net access through my fire wall (as it always did) and then nothing. Upon attempting to restart/change settings i'm informed that the program is already running on the computer (task manager confirms this, dxhr.exe*32 appears under processes) but cannot switch to it. This, i'm told, is probably caused by the game running for different user. This seems unlikely due to my being the only user (Also administrator).
I'm not sure if this is Steam/Game or PEBKAC. I could sure use some help. I've tried most of the basics, (except reinstalling as i cant find the downloaded files or creating another user account on the PC to launch it from)
Thank you for your time.
Dan
(please note, i've posted similar on Steam and Gamers gate. Any working fix will be posted in all three locations for the benefit of other unfortunates. Assuming it aint just me who's an isolated case, in which case it'll look like i'm collecting posts. Sorry for that...)

[dantheengineer]

http://www.gamersgate.com/account/me...12&tab=message

Hope anyone that needs it can see it.

Good hunting.

Dan