Why won't my Nikon D5000 take pictures?

A few weeks ago, my camera started to seize up occasionally -- it would focus and expose, but no picture was written to my SD card. This lasted for a few minutes, during which time I would turn the camera off, remove the battery, the lens, the SD card, and do any other random thing I could think of to fix it, but the camera always seemed to right itself. Yesterday though, the camera just stopped taking pictures entirely. It functions normally in everything except that the LCD screen won't show me what's visible through the viewfinder, though it still works to review pictures I've already taken and display camera settings. I've tried resetting the camera and replacing the SD card, but it still doesn't work. I have a photo assignment due for school which I've got to start work on, and I'd be crazy grateful to anyone who could give me any advice or input on what the heck is going on with my poor little camera.

My guess is that your SD card is sick. If you have another one, try it. If not, try reformatting your memory card on you computer. If that works. Reformat it again in your camera.