Upfront doesn't work freezes all the time

Dear friends, I have a problem with Upfront when I try to "edit" a page it freezes all the time, and doesn't load the upfront interface.

In other case load Upfront Interface but a BLANK Page, not my content previously update.

I have deactivate WPMUDEV, deinstalled all WPMU, reset my WP site....installed again, and starts to work very well, but when I tried to edit "Spirit" Theme, again the same problem.

Please help me. Thanks. (sorry English is not my native language)