This happens to me all the time. If you roll over something that comes up with a description box it has a chance of not going away. I used to get this all the time from the sound *on which seems to be your issue too, so I just muted the entire miniclient instead so I never had to roll over it. It does come up really often in mines though, the boxes for ores will be in the center of my screen for a while.

If you refresh the page it goes away.

Are you the only one in your GNW? Why not ask your group who you're against?

When a menu gets stuck on your screen it's only you that is effected by it. Everyone else in your group can see it just fine.

As someone who also deals with this menu not disappearing issue all the time and is also a group leader, you're making a very big deal over an incredibly minor problem. Not to mention the menu box isn't even completely opaque, you can read TheGods through the box. :P