I'm running OS X Lion 10.7.2.
I had the exact same problem - but then I had a gut feeling that Apple was being a pain in the ass again - so I disconnected my external DVD-drive and viola, all he export options immediately are available again.
Thanks apple for being so restricive with the computer hardware and software we buy from you - so much so that you feel threatened by an external LG DVD burner drive. (because the internal one is horrible I might add).
How exactly am I supposed to sell BLU-RAY disks to my clients if you (apple) don't even have that option for us. (hardware wise). Its all a form of control, they say they want to save us money from licensing fees - but this is coming from a computer company that charges 5x the going rate for ram, just as an example.
I like a lot of what Apple is about, but the stick up their butt is something I absolutely hate. They are turning a lot of clients away because of this, and no matter how hard they try, people are going to want DISKS, not just streaming content... partly because we are not stupid, and partly because even if we are willing to pay you the monthly service fees to see/use our own content, it doesn't work all the time- everywhere (airplane for example).
I am sure its not socially acceptable to speak out about this stuff, I am not sure why though, we purchased these machines, they belong to US! What we want to do with it is our business. You can make suggestions, but it would sound crazy if lets say a car company told us we could only go to six flags, not to DisneyLand - no matter who they are in bed with - once I buy the car- I will drive where I want- and the same goes for computers!
My suggestion is to disconnect your external devices momentarily, save it to a folder, then reconnect and burn as you please.