I tried it in Firefox and Safari, and had the same issue: Admin pages all work fine when I've deleted the plugin entirely, fine while Jetpack is uploaded via FTP but inactive, breaks admin plugin page when I attempt to activate, and then all other admin pages are broken after that attempt to activate JP.
Firefox just shows a blank page with this address (same as Chrome does) in the address bar: http://SITE/wp-admin/plugins.php?activate=true&plugin_status=all&paged=1&s=
Might be a conflict with another plugin? I don't have any fancy java running in the theme or header or anything like that. Akismet, IntenseDebate, WordPress.com Popular Posts, WordPress Firewall 2, Flickr Draft Post, and a few others that are inactive.
S'pose I might upload Jetpack, deactivate all others, activate JP and if it works, activate other plugins one by one to see if that's the source of the problem?