How to remove my hardback case from my iPhone without cracking either of them?

I've got an iPhone 3G and I got a hardback case that clicks on from the sides (Not one of those where you click the front and the back) I'm having trouble taking it off: P Since it's plastic, it's taking alot of cracks through the sides, and I don't want to break it. Also, I Really obviously don't want to crack my iPhone, thing is, I've tried using a stick of metal to unclip it, but when i was sliding it down the side, I cracked the part when you put the charger into, it still works, and so does the iPhone (so far) but I don't have any idea how far up the crack has gone. Does anyone know any youtube videos or just any kind of tip that could help me get the case off without cracking either the case or my phone?

Personally I'm not sure but I did find u a vid:3 I hope it helps somewhat.