I’m using 2.69, in the VSE, using a .png image sequence with alpha.
It doesn’t work with proxy. 
(I’m guessing because proxies are .jpeg’s)
Set to alpha-over, it shows white crap where image below should be.
Works fine WITHOUT proxy, of course. Is there a work around.
Any ideas from all you smarty-pants out there in blenderland?
Thanks in advance for your time and consideration!
Jay