Problem uploading sketches

I'm using a Arduino Mega 2560. Programming it with Arduino 1.6.7 .Upload process stucks at %99. I used my board for a couple of weeks. Yesterday i drived a Servo with 9V Battery using a DC-DC converter. I encountered this problem after that. Arduino Mega 2560 is selected as board, ATmega 2560 as processor, COM5 as port and AVRISP mkII as programmer.Whenver i try to upload a sketch(no matter what the sketch is even the empty one) i get "" avrdudde:stk500v2_ReceiveMessage():timeout "" message couple of times then ""avrdude: stk500v2_getsync(): timeout communicating with programmer"" message. I also cannot burn my bootloader. This message occurs ""avrdude: usbdev_open(): did not find any USB device "usb"""