I'm having this same exact issue but there was no resolution posted here... just that it now works. I've looked through my config files over and over and can't seem to find what I'm missing. I"ve read probably 10 different threads (over two days now) on this subject and no matter what I try I can't get it to work. It says it changed but it doesn't... it even logs that it was changed.
I'm using Bluehost with cPanel 11.32.3 (build 21), roundcube 0.8.1, and cpanel 2.0 (the one that came with roundcube) If I try the "new" cpanel.php used in all the threads that have success, I get an error message, as seen at the end of the error log file
ANY idea what's going on here? Thanks!