MyTouch 3G Slide Won't Charge OR Turn On

[cowhugging]

Hi, my MyTouch won't turn on. I accidentally pressed my Pandora app in class, and freaked out so I took out the battery (CAREFULLY, mind you.) Now, I don't know what to do because when I try to turn it back on, it vibrates, but it doesn't actually light up or turn on at all. :/ What do I do?
I've tried turning it on with "Shift" and "Fn" pressed, and with "Shift" pressed, and with "Home" pressed, and "Back", and "Down Volume." Now I'm at a loss...