Are you talking about renaming or even naming tapes? Not possible within BE at all. A tape's name is given to it when BE runs a job against it.
I have seen occasional errors when trying to edit media descriptions. I think a BE service restart may fix the issue, probably only temporarily? Try toggling the "preserve description" option.
I am seeing same problem, after new BE2015 14.2 FP4 install to a new 2012 R2 Server, and migrating catalogs and database from original server. Seems to have embedded reference to original media server. Trying to toggle 'Preserve Description' gets same error. Stopped/restarted services, no change.
I just had this on BE 15 on Server 2012 R2. I had migrated from a server with a different name and been through all sorts of horrors but finally cleared it up.
1. Run C:\Program Files\Symantec\Backup Exec\ServicesMgr.exe and stop all BE services.
2. Install MS SQL Management Studio.
3. Backup the BEDB (very important).
4. I found references to the old server name in tbl.Device. Trying to delete this errors but points you at other tables referencing the deviceID. These need to be deleted first. Once cleared up, everything went back to normal.
I also had problems with a reference to the b2d device that I had to remove from the database and could then re-add through the GUI.