I was just having a play with a few things in Opus and inadvertantly dragged and dropped a folder on to a user-defined button I have set up for going straight to my VS2008 programming projects. (Go "d:\Documents\Visual studio 2008\projects").
As a result of the above action the folder I dragged disappeared from its usual location and had me sweating for a while as I couldn't locate it 
I eventually found the 'lost' folder inside the ...Visual studio 2008\projects\ folder.
My question is, is this behaviour by design or a bug?
What I have noticed is I can't drag a folder to the toolbar to create a shortcut button (get the 'not possible' mouse icon), but I can drag a folder to any button on the toolbar.