On the 10 FEB, you installed Flash 10,2,152,26 and IE8 says Shockwave flash object is enabled, internet security is set to default and video plays OK. But the format buttons that add HTML code to text to post on Guardian threads no longer work. Their Help is not aware of a problem but has details. Uninstalling the latest IE8 update, KB2482017, did not help.
Norton Internet Security (2011?) is Version 184.108.40.206.
Windows (Vista HP) Update has installed several other updates, 10 FEB. Could it have set a kill bit? I am not keen to edit the Registry but a System Restore to a Windows Update Restore point is the next but one option.
Java(TM) 6 updated to 23 on 10 FEB. It set the most recent Restore point!
I took my advice and System Restored to the Windows Update Restore point but to no avail. When I had reinstalled the Windows updates and updated Flash, I noticed the Guardian pages were running in IE8's Compatibility mode. When I turned this off, their blog text formatted OK!
I can't get Guardian User Help to admit why this might have happened and it no longer does,
I regret raising this problem in this forum.