Anyone having problems with tail-lights?

I was pulled over a couple of weeks ago with my driver's side tail-light out. When I got home I tapped on the clear plastic housing and it turned right back on. Strange, I thought.

Last week the same thing happened with the passenger side tail-light: Not working, tap-tap, working.

I haven't torn the back up to install any new audio equipment or anything like that, and I'm not hard on the car (and it's never had kids in it climbing around in the back). Basically, there's no reason that I can think of for this problem.

Anyone else having similar experiences?

Thanks.


(2004 Prius, purchased in 11/03, package 9, ~45,000 miles)