I'm having an issue with the new ACL editor in the development version of DW when used under IE 7. I have just tried it with a fresh copy of 2008-03-03, and the problem persists.
After adding several Wiki pages, if I try to go into the ACL editor on IE7 (or even IE6) and click on the "+" beside a Wiki namespace, I am unable to open the namespace and view the pages, hence unable to change the ACLs. If I do the exact same thing to the exact same Wiki under Firefox/Seamonkey, it works just fine. I had emailed the list, and didn't get any feedback, but this is tested on the latest development version, and two separate PCs, so the problem should NOT be mine.