That's one of the reasons I got a Sony, and then a Kindle, after first getting a Jetbook. I've never had to reset the Sony or the Kindle, but the Jetbook is twitchy. It'll be working fine and then unexpectedly freeze up. What generally works for me is to both replace the batteries (mine's a Jetbook Lite) even if there appears to be plenty of charge left, and then do a reset. This reader is the one that I loan out, but that means that unfortunately it is sitting unused until I get it back and get it going again, because my family members are usually afraid they have "broken" it and don't want to make it worse.
I don't know WHY it does it, though.
