Nokia :: E72 Memory Card Not Supported

I have an E72-2, when i bought it, the phone was without a memory card so i purchased a blank one. Lately i am having repeatedly a message on the screen saying "remove memory card and press ok". I called nokia care and they told me to format the memory card which i did but still having the same problem. I tried backing up, formatting and then restoring many times : still the same. so i emptied every thing from the card : removed installed apps and music files and pictures and used the phone for a couple of days , everything was ok. Now i put back the music files on the card (through usb connection) and re-assigned ringing tones, the problem appears again and the phone is not reading the card (it's there but it's like blank) like it's rejecting it.

My question is : is the problem in the memory card (corrupted, defected) or in the phone? if it's the card I don't want it to damage the phone, should i buy a new one to resolve the problem? At nokia care they told me that just formatting the card will make it as new, is that correct?