iMac not reading ANY peripherals. Mouse, keyboard, remote, anything.

Just like the title says. I have an Intel iMac 20" 2.4 GHz with 2GB memory. Running latest version of Leopard. I came back upstairs 15 minutes ago and suddenly the thing won't read ANYTHING. the only button it responds to is the on/off button. for whatever reason, it WILL read the external monitor, though. but not the buttons on that. Please help. Any suggestions? I really, really need it to be working right now. BTW: I'm just out of Applecare warranty. I'm ready to kill something here.

Edit: I've tried multiple restarts.

edit: is there some way I could buy applecare post-mortem and apply it before going to them? what's the deadline after your purchase date for buying AppleCare?