I’m having the same issue as the one described here (http://ellislab.com/forums/viewthread/186154/) with the exception that changing ‘Require IP Address and User Agent for Login’ to No hasn’t helped the issue at all.
I’ll quote from the above-linked post to explain the issue since it’s identical:
The problem is when I submit any changes in the control panel, whether it’s editing an entry, editing some admin settings, or just clicking the Search button when filtering entries, I get redirected to the control panel home page without any of the changes being saved.
I noticed the problem for the first time since I moved to Thailand and am wondering if there’s some firewall or related issue (this was also discussed in the post above) that might be causing this. I’m using an internet service offered by my apartment’s management (similar to what a hotel would offer—I log in with a username and password), and am wondering if there’s some configuration with that that’s causing the problem. Any way I could test that?
I appreciate any help or hints!