Hmmm.
Well I'd ffirst upgrade to the latest itunes if you don't have the latest on run apple software updater or check in itunes itself to see if it is in deed the latest.
Is it only your iphone having this issue.
I'd firstly go to your device manager and delete every usb hub and controler you have, every one, note you will need a ps2 keyboard plugged in for this step.
then reboot.
It will force your system to redetect all usb controlers.
Failing that, there could be a couple more issues.
1,  windows is being nauughty.
2.  your usb ports in your board may be defective.
I don't think pcpitstop does error checking for usb and I am not sure what does.
From now on it could be windows or something serious.
I'd firstly go to your manufacturer's website and get the latest driver for your usb.
generally thats intel, search for and download the intel driver updater.
Install it.
run it.
hit scan.
next go and wait a while, and hit download.
then hit install and that maybe all that.
It doesn't detect everything, your next point is to search for manually and download the latest chipset instalation for your your processer type.
If you go to device manager and look at your cpus in processer you will probably find out what you need, and there are descriptions.
I'd then check your device manager for all your usb drivers for your hub and see what those are, search for those.
At this point though you may be better off getting someone to do this heavy lifting as we are getting into heavy lifting.
If that doesn't work, as an experiment just reformat and chances are the problem will be gone.
To be honest though it sounds like you have a board failier from first look at your simptoms.
Worse if its just your iphone it could be the iphone drivers from itunes.
I'd get someone to look at your configuration and see what it is, it could be software issues security issues or something more serious.
I had an issue with a system where ports didn't work, and it ended up being a board issue.
Boards cost a lot to replace.

Well if its just your iphone, all one needs to do.
1.  uninstall then reinstall itunes and make sure you have the latest update of it installed.
Over that I am not sure if you can do anything about it.

another tip. it could also be power draw.
remember. your eye phone tries to charge it self as well when connected to a USB port.
if the computer is poorly made.
like many laptops are, when it comes to USB.
or if you have other USB devices in use. that draws power. you'll have a hard time getting your power hungry eye fone to work. because  what basically happens is this. computer sees eye fone. says. hay who are you? fone says, well? i am a eye fone. i need power to work, i need a nice fast data connection as well.
computer says. well OK. you can only draw 500 milli    amps ok?
phone says sure. i promiss.
but then the computer says, hay wait somethings wrong here. i cant give that to you.
phone, then says. ah screw you to.
and then communication stops.
smile.
and that, folks is a ruff definition of what happens when you connect a USB device to your pc.
the pc first asks the device what it is, checks its descriptor information. and then decides what to do from there. depending on what it finds.

the more technical turm is called. Device inumeration.
such a boring term, so i thought i'd make it fun.  and put it in plain old fluffy English.
smile