Sorry to report all this, - but...
I removed all files from the Logo Playlist, to check out how best I could have only one chosen logo show continuously until the L key is pressed.
....
What a mistake to make!!!
The program now shows the 'black-hole' and refuses to run, (ie crashes), as soon as 'Clock & Logo' is next pressed.
Even deleting 9c and re-downloading MA3Beta.zip has no effect! - The black-hole is still there, and crashes a soon as 'Clock & Logo' is pressed.
.... The crystal can be removed, but not used. (Other than as a black area). - I haven't yet attempted to change anything in the registry.
BTW, - On checking the readme.txt in the Program Files\Marine Aquarium 3 folder, I find the Logo settings info is still for MA2.6
Edit:
Even after deleting all references to MarineAquarium3 in the registry, and re-downloading 9c again, I still have the black-hole lock-up!
.... How can that be!