avrdude: verification error, first mismatch at byte 0x0000 0x0c != 0x62 avrdude:

hi

i'm using arduino uno, mac osx 10.9.2.
i've experienced problem when upload new sketch, little manipulation coding. problem comes, there error:

avrdude: verification error, first mismatch @ byte 0x0000 0x0c != 0x62
avrdude: verification error; content mismatch

then when try run dc motors, rotating direction of motors messed up, it's seem program inside broad messed. i've pressed reset button nothing changes.

before error occurs, program works fine.

i'm desperate , i've tried google still can't find solution.

thanks

i have same problem starter kit first example : basics > blink test.
ridiculous.

Arduino Forum > Using Arduino > Installation & Troubleshooting > avrdude: verification error, first mismatch at byte 0x0000 0x0c != 0x62 avrdude:

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