[Zope] any known bugs wrt transactions never being committed?

In particular, I'm running Zope 2.3.1 and PostgreSQL 7.1b4, (tried both PoPy and ZPsycopg). The (very annoying!) problem I'm having is the postgres backend is blocking on a transaction that should have already been committed (but wasn't). It seems that a transaction from an earlier request is not being aborted or committed, but rather just left hanging. There are no hung requests, i.e. every page we request we get back in the browser. Any ideas? Thanks! -Randy