...you get a puncture on the turbo trainer. Just as I was cranking out a mighty 230 watts mid way through a ramp test as well.
Turns out a ParkTool tyre boot had stuck to the inner tube, presumably because it got hot, and pulled a tear in the tube. The cut in the tyre was tiny and I dithered at the time on whether it justifed a boot. Now removed and all seems well.
Give me your best, 'I wish I hadn't started this' stories.