iPod doesn't connect to itunes

Hi everyone, got a really annoying problem here: when I connect my ipod to a computer that doesn't have iTunes installed, but as soon as iTunes is installed, problem comes. The iTunes just stops working, and on the ipod's screen, the icon shifts from syncing to connected to syncing to connected and so on, the cycle doesn't stop, I can't modify the iPod from iTunes in any way, I tried this on two computers - one using Vista, the other Win7, but it just doesn't work. The thing is, it used to work with no problem, but one day, all of sudden, this happened.