Which makes me wonder.... if the only difference between the 2 boards was simply the bootloader used, why did it work at all? and why would the Duemilanove bootloader be so slow? there's no FTDI chip on board!
The only differences between an Duemianove board and a Uno board from the arduino's IDE perspective is the baud rate difference the two different bootloaders use when uploading a new sketch, and the fact that there is a little more free FRAM memory (that holds the sketch program and the bootloader code) on the Uno because it's bootloader code takes a little less space. The Duem board uses a FTDI USB serial converter chip and the Uno uses a 8U2 USB serial converter chip, but that is transparent to the IDE software and to the user's sketch code. So either board can run a 328p chip with either version of the bootloader on the chip, the IDE just must have it's board selection choice made based on the bootloader being used, not the name of the board.