It took me a long time to narrow this down. I was trying to put Marquee artwork up for a Dungeons and Dragons game, but it would always crash mame64 (current version). The marquee artwork worked fine on the other games. I narrowed it down to the filename of the PNG file; it was "D&D..." changing the "&" to "and" resolved the problem. If this is an illegal character, then perhaps a warning message could be printed in the log file indicating that the filename is invalid. That would of saved me hours trying to figure out what went wrong.
Regards,
Robert Cook