eZ Publish 3.10 User Registration
Another nice little bug stemming from 3.10 changes is that user registration is broken. It has been documented at http://issues.ez.no/11598 and seems to be related to changes to the eZUser::logoutCurrent() function.
Currently this issue is affecting this site as well as many others. The listed patches in the eZ Issue Tracker do enable registrations but in cause issues with email delivery for account activation.
I am currently looking at this issue and trying to formulate a suitable patch to resolve.
If anyone else is working on this and comes up with a solution please let me know.