[Zope] Error Type: AttributeError Error Value: __hash__ ??

Have application using LoginManager. Users log in (username and password). Data stored in Mysql. Some users get abovementioned error when attempting to log in, whilst others have no problem. No obvious discernable difference in data in database between users (those that work and those that don't). Not username/password entry problem either. What does this error message mean? Don't see anything in mailinglists on this. Don't know where else to look for this one! We're running: Zope 2.3.3 ZPatterns 0.4.3 LoginManager0.8.8.b1 mysql 3.23.31.win ZMysqlDA 2.0.6 MysqlPython 0.3.5 Using IE5.5 and Opera as browsers Thnx Gustav Franzsen Upfrontsystems Stellenbosch South Africa