Support

Hm, it sounds as if a plugin is causing a Javascript issue on your site. This means that the update to the latest Joomla! release will most likely fix nothing and that you can not perform it using Admin Tools (we need Javascript to be fully functional in order to perform the necessary AJAX requests).

You can alternatively upgrade your site manually. Just download the latest Joomla! full installation ZIP archive, extract it, remove the installation directory and upload all files to your site, overwriting the existing ones. That's it!

Can you try using a different browser or, even better, a different PC with a different Internet connection? It is possible that a browser plugin (e.g. NoScript), an antivirus (especially the crappy "Link Checker" feature of AVG Antivirus), Firewall or ISP filtering is blocking your site's Javascript.

So far we know that:
- it's not a missing file (you re-uploaded Joomla! 1.5.22's files)
- it's not a plugin (you said you tried disabling all of them)
- it's not a browser issue (you tried different computers and ISPs)
You have ruled out all sources of Javascript issues. Let's try something else, just in case.

Clear your temp directory and make sure no files are to be found in there (except for index.html and/or .htaccess). Then, go back to the Joomla! update page and retry updating your site. It should either perform the update, or throw you an error message. In no case should it just stay there, unless we do have a Javascript issue! In the latter case you'll have to do the bat signal: send me a PM with a link to this thread, your site's administrator URL, Super Administrator username/password and FTP connection information so that I can take a look.