Use of term bases no more possible

Hello to everybody! I have been facing problems with the use of Term bases during my translation jobs for a long time. Indeed, it is impossible to use any of them. Whenever I try to add a new term or to get the translation of a term I'm sure is included in the term base I receive the following message:

"Attempted to read or write protected memory. This is often an indication that other memory is corrupt" and this happens with all my term bases, Indeed, SDL Multi Term works quite well as I've been able so far to build my term bases...buy I cannot use them anymore. 

What should I do? thank you very much