I have a double light switch, two switches stacked. The top one controls bathroom lights and does not work, the bottom one controls a ceiling fan in another adjacent room and does work. We did hear some noise associated with the top switch a few days ago and now nothing. Is it just the switch or could it be a more serious wiring problem?

Could be you heard some sparking due to a loose connection of the wiring to the switch.
Did you open the switch box to have a look ?
Also smell the switch to make sure!

Success!

:)

EJ,

You need to check the wiring on the switch. Look for burnt or melted insulation. Test the connections to make sure they are not loose.

Verify whether you have aluminum wiring or copper. After verifing the switch make sure that the circuit breaker is not tripped finally check the immediate area for any GFCI outlets and reset them.