Report not showing correct data

I have a report created in the Account History Area that I have been using for several months and has been working as expected.  It shows the account ext uqe ID, account name, and several other colums of data that is found on the Account detail page (some custom and some standard).  Recently and coincendentally since the upgrade to R20, the report has dropped off some of the accounts.  The only thing I can find in common is that these accounts that were dropped have the exact same name as another account on the report although the Ext UID is