It's a function of red-eye reduction. I played around with my FZ28 a bit to see just what made it do this (i have experienced it in the past). in iA mode, things like Face detection and red eye reduction cannot be disabled. Therefore, in iA mode, if a face is detected in the scene, i get a pre-flash a little less that a second before the exposure. What's happening here is that the camera assumes that, since there are "faces" in the frame, you are taken a posed portrait shot in which the delay won't be an issue. I proved this by putting my camera into manual mode and activating the "Auto flash+ Red eye reduction setting." with this enabled, i got the pre-flash every time. So, play with the flash settings, and play with the red eye reduction settings. Based on the fact that its a polaroid camera, there probably won't be a lot there, but i suspect the Red Eye reduction setting that you said you turned off is a post-processing feature the camera applies to images, and not a dynamic of image capture. Perhaps this is, as stated by the polaroid representative, a feature of the camera that cannot be disabled.
What you may be able to do is force the flash on. I know it can be annoying, and can be easily remedied in PP with very simple software, but it may very well be something that can't be worked around in a lower end camera.
I hope this helps.