It could be a voltage level issue as RS232 specification was originally 12V and the Philips RFX is only 5 V.

The fact that the Arduino is having issues as well points me in this direction.

You might try a voltage level shifter. (search amazon) between the 2 ports and use +12V as a reference. You could also try using a MAX232 (again search amazon) and use +12V as input to that board.

I found this. Maybe it will help?

[Link: forum.allaboutcircuits.com]