I bought a copy of xenForo when it first went on sale. I had it setup on my test server. During my server upgrades and general network maintenance window I upgraded the test server and took the old one offline. I moved the test site to one of the production server. That didn’t go well.
xenForo would not run. 500 errors for everything I did. I tried to upgrade it to xenForo RC 1 and while the installer recognized the xenForo database it didn’t give an option to upgrade. I could only do a clean install.