One thing that’s bitten me is that Rails RC4 doesn’t appear to warn
you if your session contains objects that it cannot load back into
memory (for instance, if you have changed the Model in some way, or
have errant DBI connections stored in there…). In olden days you
used to get an error message, but at the moment you get a nothing in
any logs, rendered, and only the slightest hint of an error in the
form of a 500 response indication from WEBrick’s console.
So - one thing to try might be ensuring that you’ve cleared out all of
your session objects.