Could you please let me know the exact version of Lightroom installed on your computer?
Also are you connecting any external drive while working in Lightroom when the import window popped up?
I have 2015/6.1 installed. And yes, I have 3 external drives hooked up. However, they have been so for the last year and this issue has only started in the last 24 hours.
Thank you for the update, I would suggest you to update Lightroom to the latest version CC 2015.6.1/6.6.1.
. And yes, I have 3 external drives hooked up. However, they have been so for the last year and this issue has only started in the last 24 hours.
Hardware can start to malfunction. It is possible that the problem you are seeing is because one of the drives is not properly connected to the computer (loose cable, or cable not completely inserted) or the drive is "going to sleep" and then waking up. You need to check the cables and also run diagnostic checking on the drives.
One if your USB external drives is disconnecting then reconnecting which is causing this problem. If possible disconnect all 3 and test. Then connect each one at a time and test. Could also be a faulty USB cable or port on your computer.
Which type of computer are you using and the exact OS installed.