I noticed that my new blog creation wasn't working, so I thought that it might be a plugin issue. What I did to try to track down the problem was move everything out of /wp-content/mu-plugins/ and into a different folder outside the web root, then slowly ad in plugins one-by-one until I figured out which was doing it.
With all mu-plugins moved out, the blog creation went fine (this is in "Blogs" under "Site Admin" then using the form at the bottom of the panel, by the way). Finally, after adding plugins back one-by-one, I found that it was supporter that was causing the problems, so I started narrowing down the files by moving out all supporter files but supporter-framework.php and supporter-files/. This worked like a charm. So I added in each optional file one-by-one, and, wouldn't you know, it was supporter-plugins.php that was causing the failure.
When the new blog creation failed, I would experience the following: (1) fill out form fields, (2), submit form by clicking "Ad Blog" button, (3) nothing but a blank white screen appears--when view source is clicked, completely blank, (4) when I go back to the blogs list, the blog is there.
This kind of problem is usually indicative of problems later on if ignored and just worked around, so I'd like to find out the following:
1) What does the supporter-plugins.php file provide, functionality wise? Maybe I don't really need it.
2) If it's important, can I get an admin to mail me so I can give login credentials and figure this thing out?