I'm seeing a weird issue that I can duplicate all day on my own server, but never on other servers - so I'm not sure if anyone's going to be able to help, but I'd still like to figure it out, in the event anyone else needs to use a site hosted on my server. On the Dashboard home page (and only on this page!), submenus are not appearing when hovering with a mouse over (or touching on a touch screen) the top-level admin menu items.
My site(s) are hosted with anhosting. If I install WordPress 3.5-RC1 - through any method I can think of (downloading RC1 directly, installing 3.4.2 and upgrading through the WordPress Beta Tester plugin, downloading the latest nightly, etc.) - and then visit the Dashboard home page (/wp-admin/ or /wp-admin/index.php), in any browser - and then hover over top-level admin menu items (Posts, Media, Pages, etc.) - their respective submenus do not appear.
If I visit any other page in /wp-admin/ on my server, the submenus appear as expected.
If I install via any of these methods on another server (I've tried servers hosted with GoDaddy and Hostmonster so far), the submenus appear as expected.
Using Web Inspector I can tell that, when hovered over, a top-level admin menu item should receive the class 'opensub', which then repositions its submenu so that it's visible. There was a lot of good work done on this functionality recently to make the admin menu & submenus behave more consistently across various mobile browsers (see changeset #22636). I can tell that, when 3.5-RC1 is installed on my server and I'm on the Dashboard home page, that class simply isn't being added when I hover over a top-level menu item (or touch it on a mobile touchscreen). No errors are being thrown in Web Inspector, the class just simply isn't added so the submenu doesn't appear.
Is anyone else out there encountering this issue? I can't think of how anhosting's server configuration could be at fault, as this seems to be a JS issue, but if so I'd love to know what to look for. I'd be happy to give someone access to an installation on my server so you can see for yourself.