I had the same problem with the latest version, however I noticed export.php was there on the file system. I just went to http://yourblog.url/blog/wp-admin/export.php directly and that worked fine.
I found the problem. The beta WPG2 plugin was causing the conflict. When it is disabled I can edit files again. I will take it up/try the stable or new nightly version of that plugin.
I have searched through the other posts that are older. There is a ticket with this problem, however it appears to have been solved. That one also involved strange characters. I cannot edit any theme, even ones with simple 1 word, alpha names, with no spaces or special characters.
Anyone else having this problem or have any suggestions?
