This morning I received a warning chime and the message "Check Gas Cap" in the driver information display. The message shortly disappeared but a warning icon remained. I shut off the engine, removed and retightened the gas cap, and restarted but the warning reappeared immediately. After uttering an expletive, I went on my way. Shortly thereafter I stopped for coffee. Apparently the car liked being shut off for a while ... upon re-start ten minutes later, no warnings. I had fueled the car Friday and definitely tightened the cap several clicks -- I always do this because I know that if you don't, the OBD system on any of today's cars senses a leak and flashes the "check engine" light. I drove 180 miles over the weekend without incident; the tank was about half full this morning when the warning appeared. Has anybody else experienced this and, if so, was there any fix other than waiting for the system to "reboot" and hope it would go away?