I am constantly experiencing crashes (as in entire PC) when playing online, now I initially thought it was a problem with the PC ie cooling problems but I have not had a crash in any other game including more stressful games such as Crysis in or Empire total war.
My system is
i7 930 @ 4GHz
6GB RAM 1600MHz
750 watt PSU
Also there is a special driver for Bad co 2, it helps with crashes.... it is on their blog, a few months back..... www.blogs.battlefield.ea.com please note that it hasn't gone through much testing... Also, try updating the drivers to the newest version.