False low fuel reading

[humdoc]

Yesterday I was running some errands in the H2, and at one store the parking spot was on a very steep incline--I parked with the front of the H2 pointing down. I had about 1/4 tank of gas. When I came back out and started up the H2, the fuel guage needle was at empty and the low fuel warning light was on and the computer did not indicate a "range"--it stated something like "low fuel". I figured this was temporary and drove off. After about 5 minutes of driving on a level surface, the fuel guage needle was still at zero, and the warning light was on. I pulled over to the side of the road, turned the H2 off and then restarted it. Everything came back to normal and indicated 1/4 tank. Is this just a quirk of the H2 or is there something faulty with my system? Rob