look at my sig, 7900GTX, I also tried it on my server (3500+/6800GT/1gig) with the same results.   
My server install has 0 tweaks, but it does force aniso, I'll try without, thanks.  (I wanted to throw it up in my =COOP=SRV in HL.) :)   
UPDATE:   
So the problem here is ANISOTROPIC FILTERING...   
wtf lol, I turned it off, and sure enough, it starts with no problems whatsoever...  (I guess it s down to the weather/AF combination)   a LockOn bug perhaps with texture filtering?   
Thanks for the heads up.      Problem is, clients trying to join with anisotropic filterin enabled will CTD  :(