Used the automatic upgrade feature from within WordPress admin, this time.
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Previously it wouldn't work for me. Pressing on the 'update' link would show up a new page stating "You are not allowed to call this page directly". Apparently, it is an error issue with update-core.php and the fix is to disable a conflicting plugin – namely NextGen Flashviewer.
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Reason for upgrading was because the 'Featurific' plugin wouldn't function anymore. It requires 'WP Stats' to be working properly and it hadn't for the last week. 'Jetpack' plugin is the new version of 'WP Stats' and would only work for WordPress 3.0.5 and up; and so I had to upgrade.
Unfortunately, I think it's affecting the way pages load up and I keep getting blank pages – needing and requiring a "reload" to be able to get onto normal/any page now.