I have a Mac, soon the Bittrex wallet will be closed, and all XBB coins will disappear. It's funny, huh?
If you familiar with command line, you can use simplewallet --generate-new-wallet=Some\path\no\new\file to generate new wallet(address) without synchronizing the whole blockchain, i mean you can do synchronizing later.
Sorry for this issue, we working hard to improve performance.