brake and dash lights!

when i hit the brakes with my lights on, they barely light (stay bright all the time) and the dash lights come very dim, with my light off, everything works fine, it started sunday when i drove to the M&G sunday in the snow, and at the same time i lost my XM raido signal.
any one have ANY ideas?? please!!!

change all the fuses, check out the alternator and battery, check for loose wiring issues