I got this strange behavior since a few weeks.. Using XP with the right FTDI drivers I always get a "Unknown Device" error. I have to unplug and replug the device at least 40 times and by luck I get a connection.
When I got it up and running I am not able to upload a new sketch if the board was running for about 20-30minutes.
I don't have this trouble with sparkfun FTDI chip and a Boarduino..
Can it be that my FTDI Chip on my Diecimila is broken?
thanks for any suggestions!!