Error in ARDUINO+MATLAB+XBEE communication

Hey Folks,
I am trying to read the accelerometer data from the Arduino and getting the result on MATLAB. I am using Xbee for wireless transmission. I am using arduino library for MATLAB for this purpose. so when i write a = arduino ('COMX'), i get the following error:

a = arduino('COM11')
Attempting connection ........
Warning: Unsuccessful read: A timeout occurred before the Terminator was reached.
Error using arduino (line 116)
Unknown Script. Please make sure that either adiosrv.pde or motorsrv.pde are running on
the Arduino

I am not able to figure out what the problem is. Can please anyone help me out.

Thanking you,
Mohnish