Recording interrupted' when shooting videos on Nikon D5100?

I have had my camera for 2 months shooting photos and videos on a 32GB Class 4 SanDisk SD Card. The video recording has been working fine for the past two months but now I keep getting recording interrupted error message come up about 9 seconds into recording. I have space on my card for 3000 pictures so I still have plenty of space. Can anyone tell me why its giving me this error now?

Always use a freshly-formatted card when shooting video - class 6 or 10 are better than 4.

Move everything from your card to your computer, back up what you want to keep and format your card in your camera.

You should always transfer your images to your computer and format your card at the earliest opportunity - never use the card as permanent storage.

Sounds to me as if your card is too slow. Buy a class 10, 8gb should be plenty if you know how to use the card properly.