Problem with demuxing a signal in Simulink

I have a simulation for a self balancing robot with a Rate Gyro, and an Accelerometer. I've added the accelerometer to the simulation, but im having a problem with getting it to work. I demux a signal at the start of the closed loop so that i can feed one of the signals into a derivative block, however, no matter how many outputs i put into the demux, the signal i feed to the derivative block is still a 3 element-wide signal, and i keep getting error which means that it doesnt run. Is there anything that im doing wrong?

http://imageshack.us/photo/my-images/151/robotsimulation.png/

Any help would be greatly appreciated

Thanks George

[Arnaud Miege]

Can you upload the actual model to a filesharing site? It's difficult to see what's gone wrong from the partial snapshot.

Arnaud

[Kaustubha Govind]

What is the error message that you see? My guess is that a width of 3 is being back-propagated to the Demux block. In other words, some block(s) connected downstream to the Demux expect a signal of width 3. Also, what is the actual width of the signal connected to the input of the Demux block?