IPhone frozen, wont turn off, wont reboot?

My iPhone 4 was working perfectly fine until I opened the facebook app and it just froze. I tried turning it off by holding the lock button, nothing is happening. I then tried resetting it by holding down this button and the home button, and still nothing happens.
I then plugged it into my computer, with a temperamental lead, and my iTunes just freezes. I have no clue what to do, same someone help me quickkkkkkkkkkk!

A trick is to stick it in the microwave for 10 seconds, no Joke! This reboots the whole iphone, i do it all the time when its frozen, its a trick that is on apples website.

Hold the power button and the home button for about 15 seconds and it should do a hard reset, this won't affect your phone in any bad way, it will just reboot it, failing this you should a) Wait for it to respond. Or B) Try and plug it into someone else's computer to see if it does the same thing,
Hope this helps!
James.