nmap hangs on UDP detect
 

Ok once again I have stumbled across something that appears to be misconfigured in my 5 machine network.

I have 5 PCs all routed together via one router / switch.

When I execute nmap and scan tcp ports I get a report back for each machine in a few seconds. When I scan for UDP ports nmap will normally just hang... sometimes I get a list of the open ports on the router but other than that nada.

Any help, suggestions or ideas is greatly appreciated,
jpbarto