iMac does not recognize iPhone

I have had nothing but trouble with my iPhone 4 since upgrading my iMac to Lion.

Now, It does not even show up in iTunes. I get repeated prompts to enter my login/password and iTunes then crashes.

This has happened for a horrible amount of times.

Now, whether by USB or wi-fi, my iMac does not see my iPhone at all.

I have tried all the suggested solutions to no avail.

My Macbook pro sees the iPhone, so I doubt it's the phone.

thanks, tp