How to Deal with Whole DSP signals and systems

Hi All
      I had been simulating OFDM transmitter and Receiver in MATLAB . Down
the line system started crashing out as the number of variables(unwanted)
increased in number. More i try to contain the variables more do they
increase in size...
                       Is this Problem with MATLAB or problem with my
system ? Should i upgrade to higher version of MATLAB...

How one can handle the system once it crashes....

Thks