I just installed Omeka 2.0.3 and the site is set up. I downloaded a number of plugins and when I click on http://sanger.aphdigital.org/admin/plugins I get a blank white screen. All the other tabs are working. The public site is working, but the plugins are not--as I was unable to install them.
My first guess is that the permissions for the plugins directory aren't set correctly. Check to see if the server has read and execute permissions for the directory
I checked and it does have those permissions. Confusing.
hmm... were you able to get to the plugins tab before you downloaded the other plugins? If so, the next thing that I'd try to is delete the plugin files that you added one plugin at a time to see if one of them is the culprit