If it helps, when I click 0.25 cents, there is a modal popup that says "sorry something went wrong :(" I guess that is your unhandled traceback message?
If so there are a bunch of error logging services you can sign up for... or some you can download and run yourself.
After I click get that message, it appears that I'm signed out, and I have to sign back in.
I wish you luck with Gittip! It is a model I hope will become viable soon.
I wired up Loggly's Heroku app. It was really easy. I'm seeing a few "out of memory" errors connecting to the db. My current theory is that one of these at just the wrong moment got your account in an inconsistent state.
https://github.com/whit537/www.gittip.com/issues/143