What could have caused the hot and cold water to stop running in one sink, while all others are fine?
OK...I'm embarrassed. I know I said it wasn't the filter, because every three months I take of the filters and clean them with vinegar. 

I went ahead and took out the aerator assembly, and there was what looked like very thin plastic stuck in the hole in the center, blocking all water from coming through. 

A few years ago I saw similar material in my shower faucet when I was replacing it. 

All I can imagine is that some type of coating is flaking off from the PVC pipes (house is 15 years old). Is that possible??

Thanks to all for the responses...gives me some material for future issues as the home ages. :-)