When I post/edit/delete an entry, I get taken to a blank page and have to manually get myself back to the Movable Type page. Also, sometimes when I click on 'manage entries' it takes me to the manage entries page, other times it takes me to a blank page.
I had been 4.25, I upgraded to 4.26 in the hopes that this would take care of it but alas, it's still appearing.
Reported on Movable Type 4.2
Do you see any JavaScript errors on the blank page?
After two days and a ticket with my hosting service, the issue got resolved. They think it was a Perl error; but either way it seems like it's fixed now.