Maybe try starting itunes 7.3 in windows first. Then select the iphone via the usb menu. If it doesn't pop up into itunes, unplug the iphone from the mac and plug it back in. Parallels should rerecognize it. See if it pops up then. I have to do that with my windows mobile phone to get active sync to connect properly.
Edit: Just thought of something. It might be a case of the camera software takes over the iphone connection first, making it invisible to itunes. Maybe you can change the software settings to not 'auto-connect' when it sees soemthing plugged in. Just something else to try. Good luck.