I had a really strange thing on my first sample iPronto - it worked fine for quite a while, then one day when I was browsing the net it looked like it had somehow dropped color depth, to 256 colors - I saw lots of banding on smooth graduations.

I eventually discovered that pressing the side of the screen would change this back and forth between normal and "wrong". A short while later, it started flickering in and out of half resolution - eventually to lock in a mode where only every other horizontal line shows. The rest of the lines are light grey. It still worked, but was really hard to read! :-)