Squirrelmail Error: Error opening ../data/default_pref

If you get the following error when logging into squirrelmail:

ERROR
Error opening ../data/default_pref
Default preference file not found or not readable!
Please contact your system administrator and report this error

ensure that you have not enabled safe_mode globally in your /usr/local/lib/php.ini file. (set it to off).  If you want safe_mode on your domains, then enable them from:

Admin Level -> PHP Safemode Configuaration