This happened during a team death match game as a stock assault, i lobbed an HE charge point blank at someone, then the issue occured.
This has only happened once so far, I havent played enough yet to know if it will be a common occurence.
I'd rate it at a severity 3, restarting the game seems to have fixed the issue, however the game is unplayable when it happens.
Win 7 64-bit home premium, 16gb ddr3 1600mhz ram, i5 2550k cpu, dual geforce gtx 570's for the gpu, siemens router/modem combo thing from telus.