This took me a while to figure out, tested on two different machines.
when starting a custom "Forged Alliance Forever" game on any map VS a CPU (not tested with humans) and the "Spawn" setting is changed from the default "Fixed" to "Random" the game will not launch. Pressing the "Launch" button will not give any system response. Un-ticking the "Ready" button will result in your player name to be removed from the dropdown list.
Aborting the game, relaunching it and changing the Spawn option back to "Fixed" will solve all these issues and let you launch the game as normal....
since this issue is so easy to test I didn't attach any logs....