Many thanks for the quick response:

1. On the external monitor the line is 6 or 7 inches above the horizontal taskbar, and extends across just over half the width of the display. On the laptop screen the line height varies from less than an inch above the taskbar to 3 or 4 inches - and the line stretches across the entire width of the display.

2. Auto-hide was selected.

3. The line seems to appear intermittently - but relatively frequently (every few hours). It most commonly occurs when the laptop wakes from sleep mode and windows on the external monitor reposition as the displays and laptop itself wake up. Start11 also seems to briefly open several windows as it wakes up or does some kind of internal processing.  Makes me suspect the issue has to do with window resizing/positioning and Start11.

4. No animated wallpaper.

5. Variable, as above.

Ah, forgot to mention that I tried this already.

And the issue only arises when Start11 is installed. No Start11, no issue.

Purging and reinstalling now.

Looking back at these.

• Does the issue appear if you turn off auto hide? Also, do you have Windows auto hide turn on or just Start11 auto hide turn on?
• Please post a video showing us the " Start11 also seems to briefly open several windows as it wakes up or does some kind of internal processing. Makes me suspect the issue has to do with window resizing/positioning and Start11." part so we can observe what actually happening.

Thank you,

Basj,
Stardock Community Assistant