iTunes doesn't recognize iPhone!!

Hi,

I have a problem that my iTunes doesn't recognize my iPhone. Apple won't give me support on this because my provider should do that, but my provider claims they don't have to provide support regarding iTunes. I've tried all mentioned in the support section here, including turning off the firewall completely. I do have an iPod linked to the same iTunes (which according to a friend of mine could be the problem), but the iPod is recognized without a problem. I had to use somebody elses pc to activate the iPhone, and I would really love to use it on my own pc. PLEASE HELP