If ''License to version x.x is not acceptable' message is displayed when username and license key are entered to the License Information dialog, it means that you're trying to register ReSharper with a license from one the older ReSharper versions.
To use the license, you need to install the appropriate major ReSharper version from ReSharper versions archive.
You may also contact Sales Department with any questions regarding the licensed versions: http://www.jetbrains.com/company/contacts/index.jsp#contactSales.
ReSharper 6.x key is used with ReSharper 7.x.
ReSharper 7 needs to be removed, and ReSharper 6.1.1 should be installed to use this key.