Before your rage, or even fuck your computer trying to fix your lag. Be sure to check the servers ping and location, BFBC2 uses dedicated servers, meaning they will not find the optimal server for you. For example, a server with a low ping and a location near you is prefered. I was experiencing some lag, and I realized I was connecting with India, ffs, but when I connected with a server near me, I returned to perfect gameplay. One way to can check to see if it is indeed your connection, play for a few min in the campaign. Hope this helps, peace.
Knowledge is not power, rather applied knowledge is power.