Arduino Uno R3 not able to upload code

When I try to upload anything since yesterday on my arduino uno R3 I get the classic avrdude: stk500_getsync(): not in sync: resp=0x00 error. When I try to upload something the RX led is flashing 3 times, and when I press the Reset button, that does nothing. The L LED is always on. I tried reuploading the bootloader via FLIP(UNO-dfu_and_usbserial_combined.hex) I used 2 different Windows 7 64 bit computer several USB cables. The interesting thing is, that hppend while I was testing serval parts of a hovercraft that I am building, and it stopped working after I plugged in the control wire for an Servo. The same thing happend to my arduino nano v3.0 3 days ago. It does the exact same things I described with the arduino Uno. Does anybody know a solution for this?