I have a strange one. I have 3750s and 2950s in varies buildings all config'd with user ports access mode and trunked to a 3750 (dist layer)in each building. We have dhcp servers on each vlan to issue ip addresses for those segments. This problem doesn't happen on desktop pcs only laptops they sometimes don't get ip addresses from the dhcp server, they default to the 169.254.-.-. With a sniffer I see the dhcp discovery packet leave the clients pc but when I snif the 3750 (dist layer) port that connectsto the access layer 3750 I don't see the packet.