You cannot import a new version of driver SCCM if one or more driver files in the package are already imported into the site

Problem: When you try to import a new version of driver which was imported earlier , SCCM gives this error:  The selected driver has already been imported at this site.

Solution: Microsoft has launched a hotfix to resolve that issue, it can be downloaded from this location: http://support.microsoft.com/kb/2213600 

After installing the hot fix you will be able to import a new version of driver which was imported earlier .