After searching the phpbb forums for the same problem, someone else had posted that their brand new install did this. Blank Page, but the code and database were fine.
I couldn't find an error log on the server or control panel, but I gave the other suggestion from the MODs a shot.
I cleared the cache folder for DDT and DU.
They're both back.
Simple fix after all. Glad it didn't involve reloading the Database, I'd have murdered people.
Have a nice day.