Blackberry chord doesn't work!!!

Hello,
hi um i have had my blackberry for about a year now & its worked perfectly. everything has. when i wanted to transfer videos or pictures from my blackberry to my computer i'd use the chord & something would pop up on my computer that asked what to do. i'd open the file & transfer my pics & videos. now though when i put in the chord nothing comes out, i go check on my computer & it says there's nothing in there ex: please instert memory card on drive e or something when my phone is already plugged in. i don't know what happened but i really need to transfer those pictures & videos for a project! please help me figure out what went wrong. its not the chord because i tried it with another one & the same thing happened. nothing. did something change on my computer? please help me! & thank you