Nikon D90 Movie issue?

My Nikon D90 is supposed to be able to shoot for 5 minutes straight before I need to press record again. I'm in the middle of a shoot and my camera has begun to refuse to record for more than 30 seconds. I tried leaving it for half an hour to see if it needed to cool off but that isn't working. What should i do?

I have no experience with the D90 myself but it could be a lack of memory on your card or due to a low battery.
Try saving everything on your card to the computer then formatting it in the camera and trying again.

Your memory card might not be fast enough. Be sure your memory card is class 6 (equivalent to 40x speed, or 6 MB/s) or better. The class specifies how fast the card can write information.

Also, be sure you use the camera to format the memory card. Formatting will delete all images on the memory card, so be sure you have transferred all images to your computer before formatting.