Forum is full of failing Thomson boxes (well not literally lol). It's nearly always the power supply failing which manifests itself in any manner of wierd symptoms.
You can either rebuild if you have soldering skills using replacement parts sold in kit form or swap the entire PSU board on an exchange basis, or indeed send the box off to be fixed if you don't fancy doing it yourself.
The best place for information is the satcure website.
Thomson Power Supply Page
Thomson power supply notes
There is also a list of their recommended service engineers somewhere on the site if you do want to get it fixed by someone.
Edit : Here's their list
http://www.satcure.com/psu_fix.htm