"From Multimedia File" block no longer working if Simulink model opened on PC with Real-Time Toolbox installed

Dear All

I have a Simulink model (non-RTW) which runs fine on my standard work PC. When I open the very same model on our lab PC which also has an xPC real time target machine (and therefore also the corresponding RTW toolbox installed), the "From Multimedia File" block starts to behave oddly.

On my work PC, the block simply reads a WAV file, and it shows the output port labelled "Audio".

On the lab PC, the block points to the same WAV file, but the output port now shows "Video" and the model complains that it cannot find the input signal.

Is this a bug? I am using Matlab r2013a at the moment. If this is a bug, has this been fixed in a later version?

Many thanks in advance. wklai