Router stops working on switch

We have a major issue at work; here is the scenario:

Public IP: 64.xx.x.42
Gateway: 64.xx.x.41

Local IP:

Network: ISP connects T1 (64.xx.x.42) to Firewall/router >> router/firewall connects to switch >> VoIP swith >> SpamFilter >> Exchange/Network/VoIP server >> Workstations.

Rirewall/Router works for a while, users can access Internet, send/receive email, etc. After several hours (less than 20 so far) Router/Firewall stops responding (LAN port on Firewall/Router blinks RED) and we lose connection to internet / send/receive emails / remote access,etc.  No web interface to So far I cannot find a pattern, but I unplug the Firewall/Router from switch and i connect to a single PC and the red light goes away and I can access the Internet again and access firewall/router web interface.

My assumption is that something floods the firewall/router and makes it stop working on the switch, but can't figure out what it is.

We have been in this situation for 2 days now, please HELP!!
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You might be getting excessive collisions on that port. Try changing th c port it is connected to  
What kind of device is the Firewall/Router? Are there any logs created by the device that may contain the error at the time of the outage?

Also, does the device have any debugging features you can turn on and have monitoring number of collisions and other errors for a period of time?
If you haven't already, change the cable on that router port (put the other end in a different switch port also) You can do this when it happens.  

In the router, block all outgoing traffic on port 25 except from the IP of your mail server.

When it is happening, go to the connected switch and pull each cable out (one at a time - for 5 to 10 seconds) and see if the light on the router port changes.

Let us know what happens.

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NewcoAuthor Commented:
Thank you; i was able to find out by unplugging and re-plugging cable by cable.

Is all good now and we are back in business!
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