So we can (probably) be pretty certain the problem does not lie with sshd. It appears that connections stop reaching the sshd daemon altogether, and it doesn't sound like you need to restart sshd at any time.
Originally Posted by donnoit
Aug 6 03:08:00 abclinux01 kernel: [332548.338214] eth0: link up
Apart from the obvious, I'm not sure what to make of that. Is it appearing at exactly the time the network connection seems to die?
Do you have a spare ethernet card and cable you can swap the originals with to see if the problem continues?