Trying to upgrade SugarCRM CE on Windows 2008 box with MySQL. I've backed up my Sugar 5.5.0 and database, both within Sugar and by directly backing up the files. I've downloaded SugarCE-Upgrade-5.5.0-to-6.0.4.zip in readiness. I've changed the php.ini and IIS settings as recommended in the docs. I've set write permissions across the Sugar instance folders. I'm logged in as administrator.

When I run the Upgrade 'Wizard', it sits at the first page, with the message "We highly recommend that you perform the upgrade on a cloned instance of your production server first. Please backup the database and the system files (all of the files in the SugarCRM folder) before performing this operation." Clicking Next appears to do nothing but refresh the page. Looking at the upgradeWizard.log, this message is consistent:

Upgrade started. At start.php
Sat, 01 Oct 2011 04:23:56 +0100 [UpgradeWizard] - at unlinkTempFiles()
Sat, 01 Oct 2011 04:23:56 +0100 [UpgradeWizard] - unlinking [C:/inetpub/wwwroot/sugarcrm/cache/upload/upgrades/temp/upgrade_progress.php]
Sat, 01 Oct 2011 04:23:56 +0100 [UpgradeWizard] - finished!
Sat, 01 Oct 2011 04:23:56 +0100 [UpgradeWizard] - resetting $_SESSION

Why? Is there a way of manually upgrading this package? I'm fed up with fighting wizards...
Any help appreciated that will let me upgrade this system quicky.