Tom,
Sorry to hear you're running into some issues. We just released a big update yesterday, v6.5, with what should have been quite a few improvements.. both bug fixes and features.
You're encountering something we haven't seen in previous releases and didn't encounter in our extensive testing of this new release. Could you Private Message super admin credentials to me so I can investigate further. Since it does sound like a PHP error, if you have and can provide FTP credentials, that will allow us to step through our code and get things fixed up very quickly for you.
To PM me, please click the mail icon under my name to the left.
Thanks,
Alex