Currently Being ModeratedDec 7, 2012 7:55 AM (in response to amosglenn)
It is definitely possible to use USB ports while having ThunderBolt to Eth in.
The problem you may be having is the conference phone which would probably appear as a communication devices in your Networks.
What you can try is: connect both cables TB and USB
in System Preferences > Networks
Set Service Order (cog icon bottom of the window)
This changes the preferable connection device.
See if that helps - otherwise this is some kind of conflict with third party conference phone.
Post back your results.
Currently Being ModeratedDec 7, 2012 8:34 AM (in response to tzbikowski)
No, the phone doesn't appear as a network device, only as a USB sound input and output (so I guess it's a fancy speaker/mic and not a phone at all).
But... turning off the WI-FI connection seems to have solved the problem. Can't imagine why.