I had the same thing happen to me on my old computer. It actually stopped for about a minute.
It seemed as if the whole computer locked up. I took the chance of just waiting, and it paid off.
It didn't happen often, but it happened about 3 times over a 6 month period.
Now that I have the new computer with faster processor and bigger memory, my problem went away.
Basically with the new computer, I have had zero problems.