email it to me, at ss_deathrow@hotmail.com or post it as an attached file.
A quick fix to try: Go into the folder where the mission's source files are saved, back it up, and now delete everything but mission.sqm. Then, load the mission file into your editor. Save it, reload it, then save it as an MP mission and see if it works. If that works, the problem is the other files, not your mission.
What I'd recommend is to check through the mission, strip all the triggers and rebuild them (hopefully you haven't got as many triggers in your map as I do in mine).