English dictionary keeps vanishing

Hello Chaps,

On my portable TB which I have been running now for more than 2 years and has always been updated to the latest version. But either because of the latest version being 2.0.0.17 or because I have just started using Vista at home (still XP at work)I have been suffering from the vanishing English (British) dictionary. I also have the U.S. version and the German dictionary. Has anyone experienced this before?

Regards DF