Plugin Installer and Automatic Upgrades not working in WP 2.7 RC1

I’m not sure if this is a problem with the 2.7 RC1 build but I cannot get the built-in installers, updaters, and automatic updates working on my website running WP 2.7 RC1. All I get is a blank page after entering my ftp login (which I have checked for errors multiple times).

Any idea how to fix this? I’m assuming something is wrong with write permissions or something on the server. WP knows there are updates and uploading them manually through an FTP app (Yummy FTP) works fine (but is obviously a pain).

Thanks!