Current temperature is not really the issue. All models of PS3 have some issues with thermal dissipation in one way or another. The problem is that the soldier that connects the main CPU and/or the GPU to the main system board melts under overheating situations. Over time (in the case of my original launch 80GB; five years) the heated (liquid) solder moves and inevitably pin(s) will start to lose their board connections. If the PS3 firmware detects the error, it will refuse to start and give three beeps and a yellow light (both red and green LED lit, thus yellow). If the firmware does not detect a pin disconnect (most likely GPU) the PS3 will try to start normally, but would act erratically and would crash trying to run anything that used the faulty pin(s).
If you are having this error and the PS3 still boots, it may be able to be fixed by "reflowing" the solder connections, but this is only a temporary fix.
Again, I'm not sure if this is the issue you are having, but thought I'd throw in my 2c regarding what I've learned recently about PS3 hardware.
EDIT: Corrupt file system, eh? That's a pretty common one. Ups to Alamo for the quick fix post.
