Me and my partner where on Valhalla at PBB when it just stopped. Seems to happen quite often, something just trips apparantly.
Quite cool really, sat in dark for a couple of minutes and then all the lights came on and a rather embarrased looking ride op had to walk past us to restart what ever had tripped.
On good thing aboutthis as we got to go through the next area in the light and saw that a large section of the effects weren't on.
I have also been on PMBO when it stopped on the lift hill at the top. We were walked down after about 10 mins. Damn fine view if a little cool.