i got the same error on version 0.4b
last 10 lines of roundcube's error log
[01-Jun-2010 20:13:10] MDB2 Error: no such table (-18): _doQuery: [Error message: Could not execute statement]
[Last executed query: PREPARE mdb2_statement_mysql_362854e01e622c9eadb19f5de03f3f93df46f31aa FROM 'SELECT * FROM contactgroups WHERE del<>1 AND user_id=? ORDER BY name']
[Native code: 1146]
[Native message: Table 'roundcubemail.contactgroups' doesn't exist]
[01-Jun-2010 20:13:10 +0800]: DB Error: _doQuery: [Error message: Could not execute statement]
[Last executed query: PREPARE mdb2_statement_mysql_362854e01e622c9eadb19f5de03f3f93df46f31aa FROM 'SELECT * FROM contactgroups WHERE del<>1 AND user_id=? ORDER BY name']
[Native code: 1146]
[Native message: Table 'roundcubemail.contactgroups' doesn't exist]
in /var/www/html/roundcube/program/include/rcube_mdb2.php on line 272 (GET /roundcube/?_task=addressbook)
here's how i nailed it:
* note that i'm upgrading from 0.3.1 to 0.4b
i go to roundcube's installer folder (copy it back from tarball if already deleted it)
there will be updated min.inc.php and db.inc.php, replace it with the current one, note its permission bit
uncomment everything in SQL/mysql.update.sql except for your last version ie: i'm "upgrade from 0.3.1"
finally run
mysql roundcubemail -u roundcubeuser -p < /var/www/html/roundcube/SQL/mysql.update.sql
if your roundcube database user is roundcubeuser