Interesting error. I have some quick questions that will help find a solution:

1. Have you tried removing the foreach loop after DiscoverPeers returns, does the error still occur?
2. Odd that the error in thrown by System.Diagnostics.Debugger, have you tried running in release?
3. Why is peer discovery enabled for TCPPortScan but then you use a UDPBroadcast discovery mode in the next line?
4. What level of NetworkComms.Net license do you have? If you have Indie/Enterprise with access to source I could recommend some quick fixes without having to send you a new binary.

Marc