업로드가 잘 되고 있었는데 어느 순간부터 안되기 시작하더라구요...이런 오류가 뜨는데 어떻게 해야할지 모르겠습니다.

스케치는 프로그램 저장 공간 1,114 바이트(3%)를 사용. 최대 32,256 바이트.
전역 변수는 동적 메모리 9바이트(0%)를 사용, 2,039바이트의 지역변수가 남음.  최대는 2,048 바이트.
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x51
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x51
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x51
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x51
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x51
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x51
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x51
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x51
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x51
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x51
보드에 업로딩중에 문제 발생. 다음을  참고하세요. http://www.arduino.cc/en/Guide/Troubleshooting#upload