Wordpress 2.1 is out, so I'd hold off on the 1-click until they update it. Or you could just manually install it using WP's installation or upgrade instructions.
I think something changed with the database since the 1.x versions, but I don't remember if it was structural or if there were field name changes.
If something goes screwy, I'd run /wp-admin/upgrade.php and see if that fixes it.
Personally, I'd go ahead and upgrade your current installation, then go from there.
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