Programming is not responding (no replies)

Hi,
I have just completed bulding my melzi,we've got Burn the bootloader to it, an everything works fine, but we've got problems to upload the Marlin to it.
when uploading to the board, the code is compiling in Arduino, and after a while, we get this errror (on ubuntu):

avrdude: stk500_recv(): programmer is not responding

* on windows, we've got this error:
avrdude: stk500_getsync(): not in sync: resp=0x00

Would you have some advices for us to upload arduimu firmware?

Thanks a lot,