4g sandisk (wont format)

My memory card used to work fine, i put videos and music and pics and all but then all of a sudden it just stopped. it says it needs to be formatted. everytime i try to format it the windows says "windows was unable to complete format" then i tried the panosonic formatter and it says "write-protection is on" even though im sure its off. i need help i been trying to format for man than a month now!!!!! I've been using this memory card for almost 3 months now and have not had trouble adding music or pictures to it, i did it about 2 weeks ago. But now everytime i try to add music to it it says "The disk is write-protected" and i have tried everything that i know of to try to fix it but it won't work.