Not at WDW, but at Disneyland. I got there in the morning and headed over to Space Mountain, after about 10 minutes in line, it broke down and the line was cleared. SoI head over to the monorail just for a quick ride...yup, it had just broke down as I got in line. So I head over to the Matterhorn...you guessed it! Broke down. At this point I am extremely aggravated, so I go over to Alice in Wonderland. And wouldn't you know it, broke down! At this point I am livid, so I head over to City Hall. I am given three FastPasses for Disneyland and 1 FastPass for DCA for my inconvenience. So I head over to Spalsh Mountain and, well, you know it! Broke Down. I prcatically storm out of the park, go to DCA, use the one FP three times (the CMs let me keep it each time). It was just so annoying.
At WDW, I've been evacuated from Test Track, and had a lights-on ride at Space Mountain when the other track broke down. At DLR, I've been evacuated from the Matterhorn twince and from Buzz Lightyear's Astr Blasters twice.