In Canada, you're limited to a maximum of 12 devices (any combination of receptacles & lights) on a general lighting circuit.

It depends on how many lights there are. There is no limit to receptacles in US residential installations, but lights are limited to their capable wattage and the size circuit they are on (15 or 20 amp).

You say you had a new panel installed? Is this a new house? Or is the house existing and just a new panel was installed?

It's on a 20 amp circuit. This is an existing house being completely re-done due to hurricane Katrina.

The reason I asked about the house is because you stated a new panel, and then that one breaker kills all the lights.

The new panel has nothing to do with the the branch circuits and what they control.
Unless of course there were double taps in the old panel that were separated in the new.

The house is supposed to be completely re-wired. They removed the old box, installed a new one, new wires were run throughout the house and connected to the new box.

The concept of ALL ceiling lights being on the same circuit breaker switch makes no sense to me. If you need to work on a ceiling fixture in ONE room (as it's getting dark out), the entire house would have to be without ceiling lights just to fixe one room. I don't get it.