I think karma (in a bad way) exists, as I was telling our drummer about this thread on the way to our gig last night and we we saying we've got off lightly compared to some of the stories here... so guess what? It was out turn last night...
Firstly our lead guitarist amp failed 4 songs in - the only time he didn't bring a spare because he was car sharing with out other guitarist... fortunately one of the audience (who plays in a Bowie tribute band), went home and lent us his spare. Lucky or what? At this point my phone in my pocket managed to dial 999 twice - it turns out Iphones can be fired up without human intervention when performing.... Then the singers wireless mic started weird feedback hums at random, then the other guitarist broke a string, so one song was bass, drums and 5 of the usual 6 strings whilst amp surgery was talking place...
The second set started ok, then the 2nd guitarist's IEM's stopped working, then to top it all about 30 minutes from the end I got a huge nose bleed that covered everything (shirt, jeans, shoes, bass). It's bloody tricky to play and sing with blood and snot adding to the rock and roll look...
Oh well, hopefully that's our chunk of chaos this year, but you never know these days...