Inspiron 1564 running Windows 7 64 bit - Blue screen 9f when closing lid to into sleep mode

My Inspiron 1564 running Windows 7 Home Premium 64 bit crashed when I went into sleep mode. When I reopened the lid after returning from the restroom, I got a "Windows did not shut down properly" message. When I logged into Windows, I got a "Windows recovered from an unexpected shutdown", program Bluescreen.exe, code 9f. I'm guessing it has to do something with sleep mode/hibernation. What should I do?