It's still showing the screensaver after the hard-reset?
But, yeah, that sounds like a battery/charging issue.
Just for completeness sake: do you happen to have inordinately large book files?
Nearly everything in the 'get the cover of the book' part of the SS hack is tweaked to just die after a while in order not to hog the battery in case of problems, but there might be a way to DOS it with a very, very large file if python and/or the kernel's OOM killer is being stupid. Although last I checked, everything died correctly in such cases.
That said, if the screensaver you're seeing is accurate (ie. it's the proper cover of the last book opened), then this point is moot
.