Cod4 xfire exception

Question

when i play cod4,,after about 15 mins i get an xfire exception error,ive tryed all sorts but still no further with my problem,i can play half a game but when it comes to swapping sides i get the error,,cod2 is fine,,and any other games,,can any body help me plz,,ive tryed asking xfire but they say it's an activision problem not there's...so i'm now stumped....arrrrrrrrr...