I followed the usual procedure to move a 1.6.8 site from one domain and webhost to another domain and host.
e.g. Imported the database backup without incident, uploaded the files, adjusted directory permissions, changed config.php, re-oriented the CP to the new Themes location, updated URL-based variables, etc.
When both the public- and CP sides of the site were working as before, I noticed that some images weren’t displaying properly that rely on the imgsizer plugin. They were visible in the site files and the CP, but not appearing in my public pages.
While chasing this culprit down, I briefly thought I might need to re-upload and rebuild my image thumbs. I did this with one image as a test and the entry edit panel displayed a blank white screen when I saved. I eventually discovered that the plugin’s directories hadn’t taken the new permissions. So I fixed that and everything worked, EXCEPT the single image that I’d uploaded as a test. Its thumbnail wasn’t prepared successfully.
Right about then, I logged out of the Control Panel. Now I can’t log in: each attempt simply clears the login form and returns me to the login page. If I use an incorrect password, a password error message appears, but otherwise it goes nowhere.
I added the “S” directive to my config.php, deleted contents of the Cache directory, killed my browser, etc.
The public site is still running, but my CP is resolutely ignoring me. What do I now?