My iphone 3gs won't turn off?

Ok so i cleaned my iphone 3gs about two hours ago and now the turn off button on the top righ corner won't work.
I've tried clicking it and holding it, i even tried to force shut it by holding the home button and turn off button at the same time but it won't work, it just sends me to voice control.
EVERY thing else on the iphone works EXCEPT the top right button that turns it off.
I was wondering if any one of you guys know how to fix this?
I would really appreciate it if you can help me!

The hard reset what you basically did does work but what you need to do is hold down the power button then the home button. If that doesn't work try them at the same time or the home button then the power button