yes , this sounds very similar to the problem that I had with my 2 day old ipod. I took it back to the shop, they gave me a new one. I had only been using the new one for a day, plugged it in to my mac and had the same problem, the finder and itunes were not recognising it.
I have since been told that it is caused by a faulty firewire port, that was causing a power surge, and damaging the ipod. Am now on my 3rd ipod that seems to be working fine, haven't plugged it into the suspect mac and everything is fine. so far....