Handspring Prism question

I have been offered a Handspring Prism, and am keeping it for a few days to try it (for those interested, link here).
However, sometimes the screen flickers very, very quickly. It happens every so often, with intervals between 1 and 5 minutes, more or less.
I have a question for Prism-owning Dopers: is it normal? I have to say I suspect it isn’t, and up to now I didn’t find references to this in the documentation - or maybe I just missed the reference.
What’s your input on this?