Always needing to restart with Firefox.

As I'm surfing on Firefox, I often find it necessary to restart the computer (MBP mid 2009) in order to load media laden webpages like MSNBC or Amazon. I've tried cleaning the cache, increasing the cache, etc. but to no avail. Any ideas as to why this is happening and/or what to do about it?

Is your Firefox browser the most up-to-date?
Mozilla | Firefox web browser & Thunderbird email client
If so try re-installing it, more than likely something wrong in the system files for the program.
Hope this helps

- Simon