drivable vehicle problem

I just tried to put a drivable vehicle in my hl2dm map and as soon as I
put it in (along with a non-drivable apc and a spotlight, but i doubt
those are the problems) my map started failing to compile. When i
click "run map" from the file drop down menu it makes an error sound
and closes. It gives me no message other than what I can see in
the console briefly before the game closes. it says something
like "failed to load server" or something. Why would this be
happening and what might I have done wrong with the drivable buggy?

I don't think I've ever heard success stories of vehicles in
multiplayer maps. I don't know because I've never tried it, but
as far as I know they're not a plus.