I have been in IT for some time now and am a fairly decent troubleshooter.

Yesterday, I was working to resolve a network connectivity issue in my lab.  I have a PC/Server with an onboard Intel 882567LM PCIe Gigabit Ethernet controller and an 8-port D-Link 10/100 switch which has worked faithfully for years.

I know I need to change my cables and switch to gigabit but to date…

I have power issues where I live and have a UPS for all of my computer equipment but one never knows…

I must have moved the Ethernet cable to the switch at one point and forgotten about it because connection to this server used to work fine…

I eliminated the switch, port, cables, as potential culprits one by one… 

Electrically, the NIC even appeared to be sending/receiving signals.  I had given up on the NIC and was about to replace it when just for the heck of it, I unplugged the Ethernet cable from the switch and moved it to my Linksys router.

Eureka!  There was a hardware incompatibility between the switch and network card…

I guess still after all these years, I am still running into simple issues…  Now that I have seen it, into the bag of experience it goes ! ;)

Read the complete post at http://owsug.ca/blogs/brad/archive/2009/12/30/Weird-Hardware-Compatibility-Issue-Discovered.aspx