Are there any tricks for copy-pasting/exporting to other files?
Never did have maya be that unresponsive towards me, although I did manage to 'break' a lot more scenes when I was newer to it. I still don't know what I was doing
Have you tried selecting your objects and then doing an export? I've found this to be a succesfull method of getting objects out of a broken scene and into a fresh one, ready to start anew.
Just select the objects and export. Then create a new, empty scene and import. I guess you could probably just open the file rather than importing it, though I've got a feeling there was a trick here, and the two ways of getting the data back did not have the same result. But it's been so long I forget. to be honnest.
Hope that's of some use to you.