Blank Screen in Webmail (Horde)

Issue :

Horde webmail screen of a domain is displaying a blank screen.

Cause :

May be due to recent PHP upgrade. You may find the following entries in error log (/etc/httpd/logs/error_log)

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PHP Fatal error: require_once() [function.require]: Failed opening required ‘Horde/String.php’ (include_path=’/usr/share/psa-horde:/usr/share/psa-horde/pear:.’) in /usr/share/psa-horde/lib/Horde/Browser.php on line 4

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Fix :

Edit /etc/httpd/conf.d/zz010_psa_httpd.conf
Replace all occurance of
php_admin_value include_path “/usr/share/psa-horde:/usr/share/psa-horde/pear:.”
to
php_admin_value include_path “/usr/share/psa-horde/lib:/usr/share/psa-horde:/usr/share/psa-horde/pear:.”

Restart Apache

Reference : http://forum.parallels.com/showthread.php?t=76327