Then it won't be the capacitors bulging due to age. That's not to say that the box isn't faulty though and, if it is, it should be returned to the suppliers for exchange or refund.
To see if there is new firmware you will have to go to Thomson's website and look for downloads there. Compare the dates and revision number with what is installed in your box (you will probably find that information in the set-up section of the box menu) and then follow the instructions for updating the firmware if there is a newer one available.
How are you playing movies? Is it through your home network of off a USB drive of some kind? If off a USB drive maybe try a different one. If off the network and, if it is connected to the Internet, look for an option to update the firmware directly from the menu somewhere.