I'd also try to disable and re-enable the com port (device manager) and also on IDE to deselect the com select (pools>port) upload then re-select. Also, try on another machine/os e.g. if your issue is win win8, go to a win7 machine and try
I tried another computer to check arduino board but it is not working. Is this problem related with boot loader?
I found some information on internet regarding this problem saying it could be boot loader issue...one more thing is that friend of mine was using board, he said IC got heated just before board stopped working...help please..
I sorted out that issue...It was problem of bootloader..I replaced atmega328p-pu ic with new ic loaded with bootloader in it..it works fine now..thanks to all who helped me...