Older code shows 'Error using mupadmex' but was working on older Matlab versions

Dear all,

I'm totally new to Matlab (not to programming), I use it because I wanted to try out this programm: http://www.mathworks.com/matlabcentral/fileexchange/10692-billiard-simulator

Unfortunatly it does not work with my Matlab 2013b Version, after picking a table (any table) and trying to run the simulation an error occurs:

The following error occurred converting from sym to double:
Error using mupadmex
Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use the VPA function instead.

With older Matlab Versions it seems to work.

Did something change e.g. variable handling etc.? I don't really know how to debug the code, as I don't see where it actually fails. I tried to use debugging mode, but as it is a GUI I don't really get how it works.

Thank you for any advice.

julian