Comment 3 for bug 803299

Same problem here:

[Wed Aug 08 17:41:48 2012] [error] [client x.x.x.x] PHP Deprecated: Assigning the return value of new by reference is deprecated in /usr/share/php/MDB2.php on line 393
[Wed Aug 08 17:41:48 2012] [error] [client x.x.x.x] PHP Deprecated: Assigning the return value of new by reference is deprecated in /usr/share/php/MDB2.php on line 2647

precise (12.04), x86_64

$ dpkg -l | grep roundcube
ii roundcube 0.7.1-2 skinnable AJAX based webmail solution for IMAP servers - metapackage
ii roundcube-core 0.7.1-2 skinnable AJAX based webmail solution for IMAP servers
ii roundcube-pgsql 0.7.1-2 metapackage providing PostgreSQL dependencies for RoundCube

$ dpkg -l | grep php-mdb2
ii php-mdb2 2.5.0b2-1 PHP PEAR module to provide a common API for supported RDBMS
ii php-mdb2-driver-pgsql 1.5.0b2-1 PHP PEAR module to provide a PostgreSQL driver for MDB2