Be carefull and make a backup bebore install
I'm sorry that a few people have had problems with new code that enabled Glossary to move to Joomla 2.5. The issues did not show up during testing. Although I would always recommend people to take care over having good backups, in fact nobody has lost anything over this problem. It has indeed been discussed in the forum for Glossary, and solutions have been provided promptly. So far as I know, nobody is having any problems with the latest code.