This happens when cloning a drive.
Delete the EntitlementDataStore.ecml file. Depending on your operating system and QuickBooks version, it will be located in different directories.
Win 2000\XP will be in C:\Documents and Settings\All Users\Application Data\Intuit\Entitlement Client\vX where 'X' is the version number respective to your QB version but not the same.
Win Vista\7 will be in C:\ProgramData\Intuit\Entitlement Client\vX where 'X' is the version number respective to your QB version but not the same