Am having the same problem on a new install.
What I think is going on is that WP admin has become so bloated that it will no longer run in the memory alloted to us by the web host.
The webhost has the server set to not display the out of memory error so all you see is a blank screen.
Check and see if your PHP mem limit is set to 32m if its not 64m thats the problem.
I have tried putting the mem bump as suggested in htaccess and it did not work when I tried to put it in config it crashed wp.
What we need is someone to build a admin section thats striped down to work in the 32m enviorment.
Right now I am backung up and installing a older version to see if I can get a smaller version to run.