Odd DHCP issues with OOB Virtual Gateway

[Michael Simpson]

I've just deployed Cisco Wireless with NAC in OOB Virtual Gateway mode  
and I am seeing an intermittent issue that I'm having a hard time  
finding the solution to.  We started noticing some machines could  
associate with the AP but would never get a DHCP address.  It was hard  
to nail this one down because it wasn't tied to any specific machine  
or network.  A machine would be working fine than all of the sudden  
loose its IP and not be able to get one back.
This issue happened to my laptop yesterday afternoon.  I had been  
connected fine all day then all of the sudden I no longer had an IP  
address and I could not get one by doing an "ipconfig /renew" or by  
disconnecting from the wireless and re-connecting.  I looked on the  
"Online User" list for the Out-of-Band users and kicked myself off and  
was instantly given a new IP address and allowed to re-authenticate  
through the NAC.

Does anyone have any ideas how to fix this?
Thank you,

Michael Simpson
Network Engineer
Utah Valley University