PXE Problem

I have a problem where an IT staff who can't get his PXE boot working. He's blaming the network. I connected a working laptop (with an OS) to the same port he was using on the access switch, which gets a DHCP address & can do whatever. It can also ping the PXE server, which is on another SVI off the distribution switch. So there's no reachability issue to the DHCP server or PXE server. However, I get the IT staff to plug his laptop into the same port and I do an embedded packet capure on that port to see what's going on in a pcap. The only traffic being sent is DHCPDISCOVER's from that source laptop to the broadcast address. It never gets a DHCP offer. I've got my helper address configured correctly (as a normal laptop on that same vlan, as described earlier, get's an IP address), so I am just completely baffled as to why when they PXE boot a PC it can't even get a DHCP offer?? Any suggestions?