Strange USB problem

Development Tools IDE 1.x
1

Suddenly I have problem connecting to my Arduino devices.
I get "port in use by another device"

The Arduinos show up with no error in Device Manager.
As soon as I plug in the USB cable, I see something talking to the
device. (The receive LED is lighting) With a USB Monitor I can see
that something is sending "QPI" to the unit with an interval of 1 second.

This makes it very difficult to connect to the device. (By Arduino IDE
or any other serial communication) But once in a while I get connect, and
then whoever is sending "QPI" is stopping, and all is fine.
Disconnecting and reconnecting the device, and its "QPI" all over again.
I tried 3 different Arduinos (two MEGA 2560 and 1 Uno), which all is operating fine on another
computer..

Running latest Arduino IDE and WIN 10 pro with all updates.
Motherboard i ROG MAximus XI Extreme with latest BIOS.

Been struggeling with this for a week now, so my hat off to anybody with a solution or any help.

Regards svein

2

Your first steps would be to rule out any other software that may impede serial comms.
Blue tooth, other serial monitors etc.
You might have to check in your start up list or even services list for that aspect.
Task manager will let you see and stop anything you may suspect.

Do they show up in COM & LPT or some other category ?
Should be COM & LPT.

There might be some additional steps you can try in the second link below too.

Could you take a few moments to Learn How To Use The Forum.
Other general help and troubleshooting advice can be found here.
It will help you get the best out of the forum in the future.

Bob.