sd malfunction

[Android Question]

Hi I have the HtC thunderbolt and everytime I plug it into my pc I get a "device malfunctioned stopped working" message and the pc refuses to recognize it as a disk drive, on my phone (when plugged into pc) it shows that its charging but does not show that it is mounted as disk drive in task bar. I have taken out the sd card and put it back in already and I have changed the pc default settings to disk drive several times. I don't know what else to do please help! this just started to be a problem and now in my gallery I have duplicates of all of the pictures