Often times that's because the later games have some large dependency files that are not typically included in the ROM file, such as CHD files. If you attempt to launch the game via MAME directly on the command line, it will tell you any files that are missing.
Also - this may be connected - the update that went out today included an update to the MAME emulator (most recent version), so it's possible this has fixed some of the issues you're seeing.