My external hard drive won't show up anymore.

It worked perfectly yesterday, but today it wont show up on the desktop or in disk utility at all. I have windows 8 on a bootcamp partition in parallels. if i connect it while my VM is open it asks whether to connect it to my mac or my boot camp. If i connect it to the mac, same as before. if i connect it to boot camp then it works just fine. What can i do?

Edit: It is formatted as exFAT so it should work properly on mac and windows.

Edit: I just connected it to my roommate's laptop (also a macbook pro) and it worked just fine.