Arduino Nano TX led not flickering

I have an Arduino Nano which was working well recently and all of a sudden (I don't know the reason why) while uploading a program into it I get the following error:

stk500_getsync(): not in sync: resp=0x00

While uploading only the RX red led will start flickering for a second or so but the TX green led will not light up. I checked all the settings (and they were still like before when everythng was working well) and even tried changing the USB cable and even with another computer but still in vain. It seems that the problem is the Arduino Nano board. Any ideas what the problem might be? Or is it possible to change any component to fix it?

Check the USB port # in the drop down menu in the arduino software. Also make sure that you are not using the TX and RX pins on the actual arduino (those are used for the debugging by the device). If you have something connected to those, you will never get to upload your code. I am by no means a master, just things that I have picked up from screwing them up.