Matlab "blocked" after system generator runs (Vivado)

Hello everyone,

I have recently started using Xilinx system generator for simulating dvb communications system.

Matlab 2014b and Vivado 2014.4 were installed and everything was running smoothly with no problem.

At some point I needed Vivado 2013.4 to be installed in my laptop,and then the day after when I run the system generator the initial system generator window pops up but matlab fails to load without any error to be displayed or any other notification. Any idea on how to proceed?Is it any file that system generator uses to call matlab that needs to e configured (any kind of path misplaced)?

Regards George