you have those temps while gaming? or with normal use? they make sense for normal use and idle temps, but those are very low for load temps. I would expect the cpu to be 60-70c and the gpu to be 80-90 for normal load temps.
Another thing you may want to consider is testing the ram with memtest. http://www.memtest86.com/download.html and checking your psu's. you have 4 computers on a network at the same time playing BF3? what is your network speed. where are you located and where is the server you are playing on located? if you are in asia playing on a US server with a low bandwidth, it could be you are experiencing lag due to the long delay in communications.
I'm using the intel fan if I'm not mistaken, but I actually solved the problem.
so for anyone who is facing a freeze/crash issue with GTX 570 here what I did, my specification are not great, very normal and that's why I thought the problem is from cpu/ram..etc
anyway, the fix was by
-I increased the voltage of the graphic card by the EVGA Precision software since my card is overclocked by EVGA
-updated my PB from my game directory
- went to start -> programs files -> Accessories then right click on Command Prompt, run as administrator and type the following "bcdedit /set increaseuserva 2500" then click enter <- this is the most important step
- update graphic card driver
that worked for me and I played for at least 1h without crash so far.