Summary
Terminal Server Easy Print is not supported if the RDC ActiveX control is being run in WOW64. This will usually occur if you are running a 32-bit application that calls Mstscax.dll, and the operating system is 64-bit. This will cause the control to run under a virtualized 32-bit environment (WOW64).
In this configuration, Terminal Services Easy Print will not function.
In this configuration, Terminal Services Easy Print will not function.
More Information
Using Terminal Services Easy Print Driver
http://technet.microsoft.com/en-us/library/ff519199(WS.10).aspx
http://technet.microsoft.com/en-us/library/ff519199(WS.10).aspx