This is super frustrating - when connecting my Droid to my PC via USB, it is CONSTANTLY disconnecting/reconnecting. And it loves to do this when I'm trying to transfer files. I hear the USB disconnect and reconnect sounds at least once every 10 seconds, sometimes in very rapid succession. I cannot transfer anything anymore, and it's driving me insane. I have 6 USB ports, and all have the same results. None of my other USB devices have this problem.
As a poster below mentioned, this is a fairly common problem. My Droid will only stay mounted for 15 seconds before disconnecting, and then i get "Please insert disk' or something like that. I'm running Vista.
The rest of my phone is great (sound quality, reception, battery life, headphones, GPS), so I don't want to replace it over this and end up getting a phone with other issues. I'm waiting for a good wireless solution to transfer files back and forth. I've got Classic FTP on my laptop and some utility whose name escapes me on my Droid, but that method is slooooow.