Please verify you are using Arduino version 1.0.6. If you are not, you will receive compiling errors. You can dowload this version HERE
Under "Tools" under "Board" select the Mega 2560 Option. Click on it even if it's already selected.
Still in "Tools" go to "Processor" and select the Mega 2560 Option. Click on it even if it's already selected.
Once again, in "Tools" go to "Programmer" and select the Programmer "AVRISP MkII".
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