NOT ABLE TO UPLOAD MY PROGRAM TO THE ARDUINO BOARD.

I am new to Arduino. My Arduino was working fine until yesterday afternoon but from the evening i was not able to upload my Sketches to the board. I troubleshooted the problem in the Arduino website and i think nothing is wrong with the bootloader as the LED 13 blinks when i reset my board.

My operating system: Microsoft Windows 07
Arduino Board: Arduino Mega 2560
I was not able to upload my program to the board. I was actually working with a four wheeled robotic car before this problem occurred. i have not added or removed any software from my computer recently.

Message displayed:

Sketch uses 1,518 bytes (0%) of program storage space. Maximum is 253,952 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 8,183 bytes for local variables. Maximum is 8,192 bytes.
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer

Message displayed when i tried to upload with verbose output enabled:

Global variables use 9 bytes (0%) of dynamic memory, leaving 8,183 bytes for local variables. Maximum is 8,192 bytes.
avrdude: usbdev_open(): did not find any USB device "usb".

so,
Someone kindly help me...
Thank you.

"avrdude: usbdev_open(): did not find any USB device "usb"."

Looks like the IDE is trying to use an ISP device even though you are using the bootloader. I've read bout others having this problem before. I think the fix is to switch to a different board (like Tools->Board->Arduino UNO) and switch back.

Sorry for the late reply.
I tried doing what you said but even then it dose not work. It gives me the same error message.