I have just spent several weeks backwards and forwards with Symantec Engineers trying to determine why my Sharepoint GRT restores were working with whole SPSite objects but not with SPWeb objects contained within them. It turned out that the Symantec Netbackup Agent could not overcome a Unique entry constraint in one of the Sharepoint databases if the Sharepoint object was not 'fully' deleted from Sharepoint. The way we got success was by emptying the Sharepoint Recycle bins.

My suggestion for an enhancement is to modify the restore to perform a check on the recycle bins status for the object being restored and to either automatically delete it (if the object being restored is backed up to Netbackup) or to use another restore method which makes use of the fact that the entry already exists in the Database table.

The user account which must run the Sharepoint Agent has full access permissions to everything it could possibly need to access, so why does it ever fail when the overwrite option is chosen?

Similarly if this issue was better documented I would not have felt the need to raise this suggestion.