Mine was at Milton Keynes in 1982
As most of you will have only seen the TV version you will be unaware of this as it was carefully edited out.
However during Brian's mega solo he runs along the stage to the right of the drums and is just about to launch into a power chord when somewhere along the trail of leads behind him they come unstuck.
So he raises one arm and swings it down onto the guitar and NOTHING!
The crowd go oooooh and arrrhh and Brian looks rather bemused as roadies rush around trying to find the break, after what seems like hours (was probably two minutes) they find it and all is well.
Brian continues where he left off and shows what a professional he is!
Wondeful stuff and very funny.
Mine's from Milton Keynes too, before Queen came on stage, one of the support acts (Teardrop Explodes) lead singer Julian Cope, had the cheek to say to 40,000 Queen fans, this is the best record you will ever hear, at that somebody threw a toilet seat at him.
I'll give Julian Cope his due - he got a similar hostile reception at Elland Road, He taunted the audience with 'You're all philistines'. he tried too stare down an audience member who had climbed on top of someone else's shoulders and was promptly hit by a large bottle full of 'liquid'.