blackberry help

ok ok heres the deal i have a blackberry 8100 edge and i just got a 4 gb media card but when i put it in and go to setting> media card> it says one is not present and it works on my dads phone the media card is

"4GB Micro SDHC Class 4 Flash Card" by PNY

Turn the phone off, put the card in, phone on, try to format the card.
Or try a smaller GB card.
Is your dads phone the same? If so, your phone is NG.
Also see this post:
Transfer custom Ringtones to BlackBerry