You may have to add a registry entry to re-enable this functionality. I just upgraded to SP3 and found using "Process Monitor" that an Internet zone policy was being checked in the registry that doesn't exist. No entry, no policy, so no authorization to drag/drop.
In regedit, go to HKEY_CURRENT_USER/SOFTWARE/Microsoft/Windows/CurrentVersion/Internet Settings/Zones/4.
If there isn't an entry named 180D, then create a new DWORD entry named 180D and set the value to 0.