I ran memtest+ for 9 hours with no errors, so I uninstalled and will reinstall.
Did it, not good.
Used instruction in wiki (rpm -e tf-b4rt smeserver-tf-b4rt) to uninstall and dropped database using phpmyadmin.
Reinstalled as per wiki, apparently ok.
So I'm able to log on as superadmin, update various settings but when I try to go to the home page, I get the cannot connect error message.
Time to raise a bug?