Library error when two versions of matlab are installed

The system I'm working on seems to have two versions of matlab, 2009b and 2011a. I'm using the Curve Fitting toolbox, defining a general model, and trying to make a fit. When I try to fit data to the model (I can define the model just fine), the newer version of matlab, 2011a, fails to fit, saying it cannot find libfortran.so.2. Not surprisingly, the files in its library directories (as seen by !printenv LD_LIBRARY_PATH) only contain libfortran.so.3 in the place where the old matlab version contained libfortran.so.2 . Why is the new matlab version looking for the old libraries instead of using the new ones, and how can I fix it?