I just upgraded to Firefox 4.0 and I noticed a discrepency upgrading my plugins.
After upgrading to Firefox 4.0, the website http://www.mozilla.com/en-US/plugincheck/ shows a different upgrade status than the Tools -> Addons (ctrl-shift-A) -> Plugins then "Check for Updates" option. The mozilla website will list several updates (some out of date/"Update" link, some vulnerable/"Update NOW" link, some up-to-date, and some Unknown Plugin/"Research" link), while the Plugins tab will state "No Updates" when you try to check for updates.
After upgrading to Firefox 4.0, the website http://www.mozilla.com/en-US/plugincheck/ shows a different upgrade status than the Tools -> Addons (ctrl-shift-A) -> Plugins then "Check for Updates" option. The mozilla website will list several updates (some out of date/"Update" link, some vulnerable/"Update NOW" link, some up-to-date, and some Unknown Plugin/"Research" link), while the Plugins tab will state "No Updates" when you try to check for updates.