Why can't I compose, delete, move, or forward any message?

I can read my email messages, but I can't do anything else in Yahoo mail - I can't compose, delete, move, or forward any message. It's been like this for over a couple of week, at least, and it happens regardless of which browser I use (IE, Firefox, or Chrome). I think it might have been as early as when they introduced the new interface.

I can select a message for deleting (for example), and when I hover the cursor over the Delete button it turns into a little finger, but when I click the mouse button nothing happens - the button on the screen doesn't look pressed and nothing happens. Nothing. It's as if I didn't use the mouse button - the same mouse button I used to select the message in the first place.

I've cleared my cache and my cookies, disabled all my add-ons and extensions, and checked multiple times for viruses with different programs. I have JavaScript enabled. This happens on both my laptop and my desktop (both with Win7Pro), but things work fine on my iPhone and the computers at work.

If I use the mobile mail interface on my computer it works fine, so I do believe it's the Yahoo Mail program or interface, not my machine, or there's a communication problem. When I try to change my settings (the little gear symbol in the upper right), I get a "loading" sign of a turning wheel, but they never load. If I try to move a message, the files (places where I could move the message) don't actually load up as options, and it just says "Loading" perpetually.

It's almost like the interface is stuck in a loop and never fully loading, or something. What can I do, other than switching to gmail?