I have stopped and restarted it several times.
Perhaps I will try again.
ok and you have stopped and restarted the P2pool?
Of course.
I don't know what happened.
It was working great then just started failing.
hmmm very strange... have u got the logs of all the shares submitted by users... i'd try taking a backup of all of it and trying a fresh install of the p2pool and see if it can run... that would let you eliminate something changing on the server where it is running... if u using a hosting company or something for your server they might have not liked the traffic coming through... so may have blocked a port or put some firewall permission...
failing that it would seem like something has gone wrong in the code... from your screenshot it can';t get at the shares... this would suggest that maybe the files have moved? became too big and got dumped by the server? hmmm a strange one though... keep plugging away and i'm sure we can isolate the issue
edit:
oh and try what passion_LTC is saying