What version?
0.5.2
No. And it works successfully now 99.9% of the time. This has happened maybe 3 times over the last few weeks, and I've just got a new address from the customer and sent successfully (so it's not really a problem, just a mystery).
Hmmm... I tried this. Nothing showed up in notepad, and the same error occurred when I repasted from notepad.
Here's the latest address it happened with if anyone else wants to donate satoshis to the mystery:
1EUuzvpCSE6EwLhjV48egtgjBTy4Gtsjpm