It happened to me at work a while ago when some guy was doing a presentation in our auditorium. He said something about 'blinking problems' (god knows why this started me off) but i couldn't contain my laughter. The more i tried to stifle it the wrose it got and it was becoming obvious to everyone around me that i was desperately trying tnot to scream with laughter. I just went redder and redder and redder.
n the end i managed to just about keep my composure but my boss knew i was tryong not to laugh.