"File is changed : W[2007] L[2]"

I had almost exactly the same error just the other night, only different numbers, but luckily that one went away. Now there's this one. When I try to start up Crossfire, HGWC pops up, about to patch/load, but it stops at 0% and instantly brings up an error box saying "File is changed : W[2007] L[2]
crossfire.exe"

If it makes any difference, I use Avast! antivirus, Spybot Search and Destroy, and Ad-Aware (all three have real-time protection), though they've never given me trouble with Crossfire before. I haven't downloaded or deleted anything recently, so I'm not really sure why this popped up. Any help would be appreciated, thanks in advance.