We are in a similar position. As I understand if you use a Wyse P20 or zero client like it that is based on a Teradici chipse you will need to get a firmware update in order to use your reader. From what I have heard the Firmware update is supposed to come out the second half of 2011 which I hope will be soon.
We're currently running the 3.4 FW (out last week) - I presume that isn't enough?