What was the worst bug you've ever solved ?
rbritton: We set up a new network segment with multiple VLANs trunked over a fiber line.  The entire thing worked flawlessly except for one VLAN.  It turned out to be a conflict between a very strict media converter and bad ARP packet-generating code in the device acting as the DHCP server on that VLAN.  The ARP packets it generated were too short for the media converter, so it dropped them thinking they were damaged and the computers on the VLAN were unable to find the gateway.  The end solution was to go with a dumber media converter that didn't work at the packet level.  The DHCP device to this day still has the bad code.