I'm having the same problem. I use a webhost that has a lot to offer. The older version was working perfectly until they changed platforms and now the email features of the forum are causing the forums to crash. I tried the settings they said I need to use, but it's still crashing. I am in touch with them right now about that.
So, in the meantime, I thought I'd try and update to this newer version if the forums to see if I the email would still crash the forum.
I login as administrator, and when I press the ADMIN button, it forces me to re-log in and when I do, I get Sorry, only members with sufficient permission can access this page.
I want to see if the email on the latest version will work but I can't get past this screen. I got this the first time I downloaded and installed the thing. So, I redownloaded it and re-installed it. Still getting that message.