Cisco 3560G GBIC port problem

We have two Cisco 3560G switches and are running  cat-5 between them using the gbic ports (using the plug in adapters). At night the gbic's have been going down, acting like nothing is plugged into them. If i unplug the cables and plug them back in it comes up. It has never gone down during the day with high activity.

Any info or expertise on this would be greatly appreciated. There are no error or warning logs on the cisco's.
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If the interface on the switch goes down, it would record this on the console at least....     I would definitely setup a syslog to catch errors like this to help with the diagnosis.

Now if the ports are defective or thought to be defective, your cisco contract would cover the add-in modules as well (IIRC)

As for what's causing it...  first find out if the logs catch anything....   maybe the ports are being shutdown due to flapping?  

I once had a mouse in an office building that took a liking to plenum and began to chew though cables nightly....    

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Not only mice.... power dip during night can cause this as well. Suggest you look at your UPS log as well. Sometimes switches dont notice the dip, but Gbic's sometimes do.

Also try to look at known issues regarding this Gbic. I 've seen gbic related problems in certain series of Gbics in the past. Serialnumber lookup at Cisco might be usefull.
If the issue happens nightly and you have the time to do it, you could try knocking out some variables - try different GBIC slots - try Ethernet on 1 switch to GBIC on the other etc.  If its a problem you can simulate, its nice to know exactly where it is.  TAC support will most likely have you trying every kind of thing to isolate it anyway.
chemdryAuthor Commented:
Thanks for all the info guys, I'll be trying a number of combination's this week and will let you know what i find. I've got a replacement gbic and have tried replacing 1 of the units over the weekend but it happened again. I'll try replacing the other gbic and if it happens again i'll try a different port. (I'd think if it was the port there would be something in the error log. on the Cisco unit)
chemdryAuthor Commented:
ended up being the line. The gbics where fine.
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