i too am having the same problem; however, i have the ipod touch. I too plugged in my ipod to my computer a few days ago and it wanted me to download some updates. I did not have the time to update anything for i had an engagement that i was already running late for. So, i clicked some button (not sure if it was the cancel button or if it was some button that makes your computer completely ignore your ipod). From that moment on, i have not been able to have my ipod and my computer link up in order for me to add additional songs/videos/pictures as i could do prior to this happening.
Any advice/instructions for what i could do to resolve my problem would be much appreciated.