Indeed, though I don't think that had anything to do with the squeaking - one of my best mates is registered blind and he doesn't squeak on a regular basis. I think she was just a little over-excited... :-)
I thought the same smowball, purely because the questions he tripped over were quite easy. I have felt this on other episodes when the chaser has made an uncharacteristic spate of "simple" mistakes.
I'm sure they sometimes let the contestants win... the producers of the show must want some happy outcomes sometimes! I watched it once and the chaser was constantly watching the clock and taking ages to answer really simple questions!