After much testing of the save game functionality in the Game Player, it has become very apparent that many of the game and computer systems emulated by MESS do not properly save their system state. If a game is played on one of these emulated systems, and a bookmark is saved, or if the automatic "pick back up where you left off" is used on these systems, the game emulation will not work correctly.
I have added a flag that is set at compile time for each supported game system, if the game system does not support save, then no bookmarks will be saved, and you will receive a message on the orbiter stating that a bookmark can not be saved.
I am sorry about this. My goal is to systematically work on each of the supported game systems, to resolve this issue, either by patching the emulation engine appropriately, or by choosing another appropriate emulation engine.
I am currently testing each game emulation engine, and will be posting a list of game systems that will support save states properly, as well as note this on each system's wiki page. But I do make a promise that this will change, and it is a goal that eventually all supported systems will be able to save their states correctly.