This has been fixed in build 1464 available in the Beta forum.

That's new.

Did you just log it or did I not search well enough?

Pasting new artwork into the File Properties>Artwork. On the Add Artwork popup dialog, using the Delete keyboard key while editing the Image Filename, it dynamically deletes the artwork thumbnails on the File Properties>Artworkdialog dialog underneath. You can watch it happen. For every press of the Delete key, one thumbnail disappears. Once you click OK on the Add Artwork popup dialog, the File Properties>Artwork is missing those previous thumbnails, and then saving the File Properties permanently removes those artwork tags/links. It's cool if you are replacing one album cover with another but dangerous if you're unaware what's happening. Definite bug. Delete key should only work on the active dialog.

Thanks,
Pat