The only problem before this with the Singers Database has been the addition of "Null" singer's names and the inability of being able to delete them. That was fixed.
I think yours was a corruption of the file. It sounds like it scattered the data someway into different records.
The Singers Database stores in the Singers Table 3 things. A unique SingersID (ID number), Name, and date added. In a second Table called Songs it stores SingersID, BookID (from Songs Database), Key, Tempo (not used yet), and SongDate (date song was selected last).
It could be possible then that the corruption is in your Songs Database instead of the Singers Database. Did you do a Rebuild after copying the KMA files to the new drive?
I should have thought about it and had you send me a copy of your Singers Database before you corrected it, so I could look at it and see what happened. Twenty/Twenty hindsight.
Musicman144's loss of songs is a whole different ballgame as his "problem" was in Playlists and not the Singers Database. I suspect it was the same as JSN02 and not a program error. My wife has done this partly because the Skip and Delete button order was changed and she would hit Delete thinking she had hit Skip and the song would be gone. This change was added in 4.10 so is new to everyone.