udp packet loss

I've got a small 802.16d LAN up and I'm trying to figure out why I've got 80% plus packet loss using UDP. Iperf shows 10Mbps throughput speeds w/ TCP, but UDP is terrible and I don't understand why.

The SS has good power and SNR levels, modulation is QPSK or better and it's out in the middle of an empty field where there is no reflection and I'm only 500 yards away.

I don't know what else to try other than do a packet capture to see if TCP is doing a lot of retransmissions, and since UDP doesn't retransmit, I figure if the problem is somehow eventually solved, TCP performance should really improve (if it is doing a lot of retrans).

The BS is a layer 2 device and shouldn't know the difference between TCP packets and UDP packets, and there is no filtering or QOS configured, it's as basic as can be.

Anyone have an idea of what else I might look at or try out? I'm kinda running out of ideas.