Because the motion board runs it's own onboard processes, comunication between the PC and the board is message bassed. The board has a message queue which it fills up with commands sent by the PC. If commands are issued in too rapid of a sucession it is possible to fill this queue and to return error of the type you are encountering. If you are sending down a number of blended move commands in a loop please make sure to have at least 5ms between each command.
Hope this helps,
Amaury
