Code Upload Problem!!!!!!!

Hi, I am new in arduino world. I am using UNO R3 with Windows 8.1. It was working fine and all of a sudden it is having problem in uploading code to the board. The error it is showing is:

avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x64

Can anyone sort out the problem? It is not upload any example code as well.

i have exactly the same problem. posted on spanish

If my suspicions are correct you might have, somehow, corrupt your bootloader. If the bootloader is still in place the 'L' led should blink six times whenever the board is reset or powered on, have a look to see if it still does that.

If it doesn't blink the 'L' led, you will need to bootload the device using either another Arduino as an ISP programmer, A USBISP or some other ISP programming device. Let me know the outcome of the test above and whether or not you need help making the next step.

Good Luck