Unable to delete old map files

Why is it whenever I try to remove and old level ( map ) I’m not using any more, I get the message:

“some of the assets being deleted are still referenced in memory”

Nothing is referring to the map, I checked in the reference viewer. I’ve also done a ‘fix up redirectors’ on the entire folder heirarchy.

Is it ok the hit the force delete button, or is there some subtilty I don’t know about?

You should be fine using the ‘Force Delete’ option. The only downside would be that your ‘undo’-history will be reset.

I have a similar problem. However I am sure the map is not in the undo history. Interestingly if I try to move the map I get this message. Anybody got any thoughts on what might be causing this?