Hi Dan - is this new with SR14? My chat with the developer leaves me thinking this might be hard to track down unless you can find some way to reproduce it - the key is to get the text off of the command history when this occurs and I guess F2 is not going to work if there is an stuck modal dialog. But, if you can get this to happen with the command window expanded, you might see some info about an exception thrown that we could use. By any chance does the Windows task Bar show more than one Rhino icon? It could be, maybe. that there is a dialog of some kind lurking behind that main dialog.