[CentOS] Server hangs on CentOS 5.5

>The only indication that I had that there was a problem (other
>that attached systems were not accessing files) was that the
>fan(s) on the server were louder than normal.

Are you saying the fans were running faster than normal while it was hung?
Or are they louder than usual even while its running?

Fans making noise can mean the fan isn't spinning as fast as it should
because the bearing is failing. Be a good time to open the case to check to
see that all fans are working...