Network activity halts and system hangs?

I have a 2010 Mac Pro that has a strange problem and I'm curious if anyone else has experienced it. I can't recreate it on the fly and it seems to be completely random (happening within 30 minutes of a cold start or after 10 hours of running):

Without notice all network activity ceases to function, it's like someone pulled the network card. If I go into Network Preferences I still have a green line for the ethernet port (I'm not using wifi on this machine so it is disabled) and it shows an IP address (DHCP), etc. Unfortunately shortly after this happens (within seconds) I can't open up any new programs (i.e. terminal, activity monitor, etc). New programs try to open up but they fail to open, they just stay in the dock with no activity.

If I try to close some programs (e.g. mail.app) those programs never close, I must do a force quit on them. After all running apps have been closed and I attempt to shut the system down properly it just hangs at which point I'm forced to hold down the power button to shut the system down.

This happens the same way each time this problem occurs. I may go the entire day without an issue, but some days I may experience it two or three times so it's very frustrating. From day to day I have the same programs open all day so there's nothing new being brought into the mix that may cause the issue that I can see.

Has anyone seen or experienced something similar? Ideas of how to resolve?

Thanks!!

 

I wanted to follow-up on this issue. What I've done:

I reset the SMC and did a disk repair on the drive. The disk repair did find a few issues but subsequent repairs have found nothing to fix. I choke it up to me having to simply hit the power button to cut the machine off with the drive spinning.

For good measure I went ahead and ordered a new WD Black 1TB drive. This is the newer model with 64MB cache. I used Carbon Copy Cloner to clone my old drive to the new drive and then made the new drive my startup drive.

Interestingly, the same issue happened again which leads me to believe it isn't a drive failure after-all since this is a brand new drive I'm running from.

Of note, during the "lock-up" this afternoon I tried to move between different spaces in OSX. Obviously I didn't get a response while the system was "locked-up" but after 20-30 seconds the system did catch up momentarily and it switched between spaces. Unfortunately it went right back to being locked-up and I finally had to hit the power button and boot-up again so I could continue my day.

I've also been looking at the console but I really don't see anything that would signal an issue. I note the time on the OSX clock of when the lock-up happens, but there is never an event in console within 3-4 minutes of when it occurs.

Any more ideas?

Addendum:

I just noticed DirectoryService*.crash logs in Library\Logs\CrashReporter\

There are only three and I know this has happened more than three times, but interestingly there is a crash log with today's date and a crash log for the 29th and 30th of November which I also had the issue. Could they be related by chance? All of the logs have the same reason:

Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000000
Crashed Thread: 6 Dispatch queue: Kerberos

 

Yep, I'm on 10.6.5.

Yes, I have to shut down forcefully each time this occurs. The first time I had to shut it down this way was because of the stated problem however so it couldn't have been the root cause of the initial issue.

Knocking on wood, I haven't had the issue in the last few days but I haven't changed anything either.