See summary. This happens only for the player who gets the auto opened corpse window
The guilty party seems to be Component.setComponentZOrder() (eventually called from JLayeredPane.moveToFront()), which for some reason results in the said flicker when called with non-zero z-order. I have no idea why it happens only when auto inspecting.
It can be reproduced with just corpse windows too (move them so that they do not get opened on top of each other); but again only when a window is raised as a result of autoinspect.
InternalManagedWindow.raise() would be flicker free if it called setComponentZOrder(this, 0), but this would cause container windows being drawn above the quit dialog.
One possibility for a fix would be using a regular modal dialog for quiting. I think the dialog is the only reason the client uses a layered pane to contain the game screen.
You seem to have CSS turned off.
Please don't fill out this field.
OK, thanks for the error report.
Problem is now fixed in CVS.