Arduino can't Uploaded a new sketch on ESP8266

Hi.
I have uploaded a lot programs by arduino on ESP8266 but now when I want to uploaded a new program, It has some error like below, although before program still working on it, but I can’t uploaded a new program on it.
Very thank you.

Eroor:

esptool v0.4.9 - (c) 2014 Ch. Klippel <ck@atelier-klippel.de>
	setting board to ck
	setting baudrate from 115200 to 115200
	setting port from COM1 to COM4
	setting address from 0x00000000 to 0x00000000
	espcomm_upload_file
	espcomm_upload_mem
	setting serial port timeouts to 1000 ms
opening bootloader
resetting board
trying to connect
	flush start
	setting serial port timeouts to 1 ms
	setting serial port timeouts to 1000 ms
	flush complete
	espcomm_send_command: sending command header
	espcomm_send_command: sending command payload
	read 0, requested 1