At the risk of resurrecting a dead thread..
We have also experienced this with the new EliteDesk 800s on older Promethean boards which have wall plates.
Connect a different PC with the exact same Window image (we use hardware independent imaging) to the wallplate - works fine.
Tried different ports on the PC, different drivers, firmware for the 800 Elite - no dice.
Tried latest Promethean drivers, older drivers etc etc. No go.
Running Windows 7 SP1 Enterprise.
If we bypass the wallplate by connecting a 5m USB2.0 cable directly to the back of the board, then it works.
The wallplate in question doesn't appear to be anything remotely clever. It's just a male USB-B male running to a USB-B female wallplate - no active extension or hubs, etc.
Our current theory - based purely on the fact that the cabling doesn't have 2.0 written anywhere - is that it appears that the cabling used was USB 1.0, and the newer chipset in the 800 hates it.