[Phssthpok]

I've just upgraded to Calibre 4, and suddenly in the editor I see a blinking white dot at the top of the line containing the cursor. When the cursor is positioned in front of the first character pf the line, the dot is at the top left of the leftmost character in the (gray) line number column. As I move the cursor right, the dot moves right. It maintains the same distance from the cursor (so in a file with <1000 lines where the line number column is 3 chars wide, it is 3 chars left of the cursor; with files with >1000 lines it is 4 chars left of the cursor). It blinks at about 2Hz (faster than the cursor blink rate). It's only really noticeable on the gray background of the line number column, but it's a bit irritating, and I get multiple dots all flashing away as the cursor moves.

Same hardware/OS as before when I was running Calibre 3, so: Is this some artefact of the new Qt library I'm seeing, or what?