i have problem.

All is ok (game, graphics and details). But when i play 1 hour, GW crash! 1x, 2x sometimes even more... Total restart PC!

My computer:
Intel Core 2CPU 6600 2,4GHz, 8GB RAM, nVIDIA GeForce 9800GTX+ 500MB (1280x1024)
Windows 7 Ultimate, DirectX 11, ...
All my games, software (3D MAX and next) it's OK, NO PROBLEM! Only Guild Wars

I need help, thank's!