SystemIO Exception when opening RFCOMM in Mono

Question

I have a Mono application which opens a RFCOMM connection (/dev/rfcomm0) but when I run as a user, I get a System.IO.IOException Interrupted system call. I'm running this on openSUSE 11.2.

  Unhandled Exception: System.IO.IOException: Interrupted system call
  at System.IO.Ports.SerialPortStream.ThrowIOException () [0x00000] in <filename unknown>:0 
  at System.IO.Ports.SerialPortStream..ctor (System.String portName, Int32 baudRate, Int32 dataBits, Parity parity, StopBits stopBits, Boolean dtrEnable, Boolean rtsEnable, Handshake handshake, Int32 readTimeout, Int32 writeTimeout, Int32 readBufferSize, Int32 writeBufferSize) [0x00000] in <filename unknown>:0 
  at (wrapper remoting-invoke-with-check) System.IO.Ports.SerialPortStream:.ctor (string,int,int,System.IO.Ports.Parity,System.IO.Ports.StopBits,bool,bool,System.IO.Ports.Handshake,int,int,int,int)
  at System.IO.Ports.SerialPort.Open () [0x00000] in <filename unknown>:0 
  at (wrapper remoting-invoke-with-check) System.IO.Ports.SerialPort:Open ()

If I run the application under sudo, it works fine.

I have added the dialup group to my user account so I'm not getting a permission denied error.

I'm not sure if this is a Mono serial comms question or a permissions question for SuperUser.