Thanks, problem resolved from your clue about the Launching screen.
When I was moving files around Windows created a mspacman-01. LB had that file name in Launching and I had already renamed it back to mspacman.
I emptied the rom folder completely, had LB do a scan for removed ROMS to set it back to nothing, put the rom back into the folder, then closed and relaunched LB so it did a fresh scan.