vertex lock failed on crossfire date: 30 march 2011

hello everybody i have a problem on crossfire,

when i play the second game on crossfire than came a error. the name of the error is ''vertex lock failed''. please help me i can''t play crossfire anymore... (the error is a black screen with other colors, so you can't play crossfire because you can't see where you walk)

date of the error 30 march 2011

please help me i don't know what i must do!!!...