CANON G2 auto flash troubles

im having trouble with the flash on auto mode. sometimes i will take a picture and the shutter will go of at about the same time the flash does, and i do not get the correct amount of light, or any light for that matter. does anyone else know what i am talking about, how can i adjust this in auto mode, or is my camera disfunctional

I have a G2 and have never seen this problem, but I shoot in Av or Manual when I use the camera underwater.

Following URL describes common problems and suggestions:

http://www.ikelite.com/web_pages/qdigital.html