If you reinstall it should not change validation/authorization.
ADE has a way of getting authorization mixed up; if it does go wrong
ctrl-shift-D to ADE to remove old authorization (cmd-shift-D for you on a Mac)
restart ADE
reauthorize
~~~~~~~~~
You may find the old version v1.7.2 better, much more reliable in many ways than ADE2.0 which is a load of bug riddled rubbish.
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
http://helpx.adobe.com/digital-editions/kb/cant-install-digital-editio ns.html
The forum software is sometimes corrupting the link above. There shouldn't be a blank in 'editio ns.html'. The following redirects to the same page: http://tinyurl.com/diged172