Needs more testing.
test 1: Run the "loopback test" to see if the board's USB serial converter is functioning. There is a sticky posting around here somewhere. If that fails then there is not much to can do about it other then get a new board.
test2: If the loopback test is good then you have either a bad 328P chip or it needs a new bootloader burned into the chip. To do a burn bootloader one needs either a IDE supported hardware programmer or another arduino board runnning the arduinoISP sketch which then becomes a 'hardware programmer'. Probably easiest solution if the test1 passes is to just buy a $5 replacement 328p chip that already has the proper Uno bootloader burned into it.