John St, did you ever resolve this issue? I am having the same problem. I started the database upgrade, and it went okay for a while, but then it just stopped (at something like "Converted unsigned columns in MySQL database - 149/347"). When I tried reloading, I would get the "Site is being upgraded, please retry later" screen. Now here is the interesting part. If I waited for an hour or more and tried reloading again, the database conversion would start up again from where it had stopped. It would continue for a while and then hang up again. I repeated this process several times (took me all day) and managed to get through the conversion of unsigned columns. But then on the next stage of the database upgrade, I eventually stopped getting any response at all, and I got an error message not from the moodle but from my rental server. Eventually I gave up and restored my installation to 2.2 from backups. I am now trying to convert a different moodle installation, one with a much lighter database, but I am experiencing exactly the same problem. Is anybody else experiencing this?
by Henry Foster.