G-Sensor won't calibrate correctly

[armiller17]

It seemed like my calibration was a little off while playing labyrinth, so I went to the main settings to re-calibrate. When I got to G-Sensor calibration, I sit the phone on its back, and the bubbles appear to be level. Then when I click 'calibrate' the Y-axis bubble jumps to the top quickly before calibration, and remains there. The X-axis appears to be more or less correct, but for whatever reason the y-axis is not. I've only had the phone for 2 days and haven't made any major changes to the phone.

Powering on and off doesnt seem to fix this error. Any advice?

Thanks!