Well, that helps, but I was already using buttons in my test map for their simplicity. I never even got to the point of trying to trigger a multisource directly with grunts, so that was never a problem.
game_counter will work, but what am I going to use as a master for the trigger_once if multisources won't work?
Edit: That's funny, my multisources appear to work entirely now. I can't even explain it, except that Half-Life might have some kind of problem with multisources actually being named "multisource", and targeted as such. Oh man, most annoying problem ever and I don't even know how I fixed it.
Edit2: YES, IT'S TRUE! multusources cannot be named "multisource", they simply will not work. I ran the same test map, the only difference being the change in entity name, and it made all the difference. and I thought I was making it as simple as possible by naming it that. I tested a multi_manager the same way, naming it "multi_manager", and it didn't work either. Funny, I never knew about this before.