has anyone met the same problem like me?
Yes even the most cursory search shows it is the single largest problem reported.
You have either:-
- Blown up the USB / Serial port chip - does the PC still recognise it as a serial port? Is there a faulty cable?
- You have messed about with the watch dog timer and need to reprogram the boot loader - you need a programmer to do this.
- You have blown up the processor chip.