The most common case with that kind of error would be if you have a routine that you created on the MATLAB path that happens to have the same name as one of the Mathworks provided routines that gets called directly or indirectly from the code. For example if you had your own set.m routine then that would mess up many functions.
You might be able to isolate the problem if you go to the MATLAB command line and command
dbstop if caught error
and then run the model. You might have to use "dbcont" several times until you are in the appropriate openfcn and then can start seeing what triggered the error.
