problem uploading sketches

ey!

I am getting the following error very often now.


Arduino: 1.6.1 (Windows 7), Board: "Arduino Mega or Mega 2560, ATmega2560 (Mega 2560)"

Sketch uses 6,960 bytes (2%) of program storage space. Maximum is 253,952 bytes.

Global variables use 1,622 bytes (19%) of dynamic memory, leaving 6,570 bytes for local variables. Maximum is 8,192 bytes.

avrdude: ser_open(): can't set com-state for "\.\COM8"

avrdude: ser_drain(): read error: The handle is invalid.

Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

This report would have more information with
"Show verbose output during compilation"
enabled in File > Preferences.

In various circumstances, with different boards, different ports and different sketches.

I had checked the port in device manager, and I always check the board and port in the arduino IDE.

Any idea whats going on?