Mega 2560 Doesn't Respond When trying to upload to my Mega r2, it simply times out during uploading.

avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer


I tried burning the bootloader, but that also gave an error.

Error while burning bootloader.
avrdude: usbdev_open(): did not find any USB device "usb"


I can see the arduino in my Devices and Printers in control panel, so I don't think the board is burnt.  The power light also is on.  Any ideas?
I have seen this error numerous times before. I think the possibilities could be that either some external device is connected on RX, TX pins of arduino mega or mega is not getting sufficient power. Some connection from your board is trying to pull more than the limit current.

and off course the answers suggested above are also right. check out every possibility.