Labels have been working fine on my machine. Have you tried:
1. Adding a layer to a new, blank map and creating labels from scratch -- do they appear then?
2. Checking your label weights - Map ribbon tab > Labeling group > More > Weights. Each feature has a weight, are any set to 1000? Check the weight of any graphic layers, too. Any set to 'high'?
3. Turn on 'View unplaced' from that same labeling group. Are you seeing them then?
Just a few troubleshooting steps to get you started, could be something else, too.