What version of the chip ROM do you have?
You need at least to have ver. "RPC-1A03" , the original ROM "RPC-1A02" is defective.
Call Roland for the replacement
PARTS
"#02899067 -------------- IC SERIAL ROM XC17S30XLPD8C (RPC-1A03)
The driver has been tested with Windows 7 Ultimate and two RPC-1 boards connected to two VS-2480 workstations and it works well.
The limitations in the MIDI side are inherent to the design of the RPC-1 , it only supports realtime system common messages (less SysEx).