If you want to get a little silly you could really strip down anything that is on that switchport. BPDUfilter, portfast, no cdp, force it into an access port, and no PoE. In theory the port should be dead quiet in case the nic isn't liking on of those non-essential frames being pushed out.
sw mode acc
power inline never
no cdp en
spanning-tree bpdufilter enable
While that's fun to do, I'd also take a hard look at the OS you are running. You might want to try a Linux boot cd and see if you have the same issue if you are starting up from another OS.
I've also seen windows fail to correctly report the status of the LAN interface. is the port truely down on the switch or is it just that Windows is saying it's down?
Well, I'm rather embarrassed to say, it was a bad cable. Now, what are the odds of having two bad cables from a mfg.? When we put in the 4510, we bought about 100 Cat5e and I was using one of them. So, when this problem first occurred, I replaced the current cable with one from the mfg.
After trying Linux, it still didn't work. So I swapped out that cable and lo and behold, link came up.
But thanks for the tips. I'll add those to my troubleshooting tip book.