Recently, the high hats in my kitchen stopped working, even though others lights which run on the same circuit breaker are working. Don't know what to do other than call the electrician. Any suggestions? (and yes, I've changed out the light bulbs! ). Thanks.

Test or replace switch, or jump out momentarily. If all is good, and you have 6" cans, you can remove the 3 or 4 screws that secure can to housing, then pull down or push up into ceiling, remove electrical cover plate and check connections, start at light closest to switch.
If on a 3 way, check lights closest to other switch also.