My Nikon D3000 is running slow?

It runs really slow when it goes to view pictures.
Any ideas why?

Educated guess? Slow or damaged memory card.

Memory card might be starting to go bad. If you have another memory card try it. If the problem continues, then it would have to be something with the camera.

but I would bet on the memory card failing.

What is the Class of the memory card? I think you need Class 4 or above for best performance on that camera.