https://addons.mozilla.org/en-US/firefox/addon/lastpass-password-manager/ Last Pass is supposed to be compatible with Firefox 6.0a2, so Firefox 5.0b2 shouldn't be a problem. Open the Add-ons manager Tab - {Ctrl + Shft + A} - right-click that extension - use Find Updates. See if that forces an update for that extension. BTW, you must be on the Beta Channel for updates, Firefox won't be a release version for at least another month to 6 weeks. There should be a channel changer feature in the Help > About Firefox.