Hi Tony,
Is the PC handshaking via the serial cable? I seem to remember the CC100 is fairly sluggish even a low baud rates, and will pause transmission (by setting CTS low) until it processes the received data.
I dont think the CC100 can software handshake, so try hardware handshaking using RTS and CTS, or try a lower baud rate
Keep us posted
Rgds
Loko