computers cant see iphone 4 but phone will charge

I have an iPhone 4. I have 3 computers- a Mac, and a PC with XP and another PC with Windows 7. When I plug in the iPhone to any of these computers, the phone will charge, but iTunes wont recognize the phone.
-On the PCs, the computers wont recognize the phone as a device at all.
-On the Mac, I can see that the phone is connected when I go to Finder, but it is not recognized as an iPhone and the Mac prompts me to set up cloud to sync the device.
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in Windows 7,
-All of the USB controllers for the iPhone were working correctly.
-Also in Windows 7, I am sure that the Apple Application Support is installed and working properly.
-The iPod device detection (or whatever its called) is properly functioning.
-Ive tried restarting the iphone and itunes. No luck there.
-Ive tried to reinstall itunes on the Mac and on the XP PC, but that didnt help either.
Im not very ritualistic about connecting my phone to my computer. I last backed up my phone in November, so wonder if iTunes updates have surpassed the level of updating on my phone??? My phone version says its 4.1 (8B117) --whatever that means, and it says that its modern firmware is 02.10.04 --whatever that means...
I am hesitant to restore my iphone to its factory settings because I doubt that will work--how could that make itunes suddenly know that its an iphone?? Please help me! I have been working on getting this thing to sync forever and it just wont seem to work!!!
xp, 7, mac os iOS 4