I have the same or very similar issue. i have iphone 4s and windows 7. while on ios5 all was perfect. one day i updated itunes, then phone to ios6. next morning i plug iphone to computer and it's not recognized. it doesn't;t show up anywhere. not on the control panel, not on itunes, nor under system properties. the iphone does charge when plugged with USB to the computer.
things i've tried:
reinstalling ios6, since then i also performed the upgrade to ios6.0.1.
i've followed the instructions to uninstall all apple programs, itunes, QuickTime... restart , confirm all files/folders are deleted, and reinstall. still nothing.
it's very frustrating not being able to save my photos to my computer anymore, update music, nor access files on apps like goodreader and others. i didn't have a icloud sync setup and now since the iphone is not recognized i can't do it either.