I have seen similar issues where the device doesn't service traffic but u can console it and this issue is intermittent ( it appears every 10 days or so).There are quite few reasons and one of them is the link negotiation where you need to check if the auto negotiation is on on both the ports. Lets take an example where you have auto negotiation on the uplink of the first device ( router or a switch) and you have configured the speed of 100 duplex on the second device , there is a possibility of the link negotiating the speed to a half duplex and in a half duplex environment you have csma/cd coming in to picture to avoid collisions but definitely a delay in traffic , you have this issue coming up and let me tell you again that this issue is very intermittent.The second reason for this issue can be a corrupted OS.
derk, Regarding emperorz point, Check for messages similar to this:
[code:1]00:06:38: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on Ethernet0/0 (not half duplex), with Switch FastEthernet0/1 (half duplex).[/code:1]
In this case router had "full-duplex" on E0/0 while the switch had "auto" on FE0/1.
