Strange behavior

I get an issue when connecting a USB flash drive on a WTOS Thin Client using Wyse TCX Virtualization Suite running on Windows Server 2008 R2.
When connecting a USB flash drive to the TC, the drive is mapped by the TCX on the server, but I cannot open the drive. Looking at the traffic statistics I see that it keeps uploading data, and the green led on the flash drive keeps flashing.

Now, this can be fine if there is data on the key, as TCX needs to upload files on the server to make it accessible, but I tried to format the key and this is happening with the empty USB key too: it seems to be stuck uploading something that can't be there!
Anyone reported the same issue?
Any help will be appreciated.