Whats in your error log?
I take it from this that there is some table that it is missing, but i don;t know where that table is supposed to come from.
[06-May-2010 12:08:52 +0000]: DB Error: _doQuery: [Error message: Could not execute statement]
[Last executed query: PREPARE mdb2_statement_mysql_34af4524b0bf9e5893bd923d9e4dc2f51a1a8202e FROM 'SELECT * FROM accounts WHERE user_id=?']
[Native code: 1146]
[Native message: Table 'roundcube123.accounts' doesn't exist]
in /mounted-storage/home49b/sub002/sc29675-EMTT/www/webmail/program/include/rcube_mdb2.php on line 269 (GET /webmail/?_task=mail)
[06-May-2010 12:11:26] MDB2 Error: no such table (-18): _doQuery: [Error message: Could not execute statement]
[Last executed query: PREPARE mdb2_statement_mysql_3167cd130d31ebbb2b10d8729ef25ff76d8c98ba2 FROM 'SELECT * FROM accounts WHERE user_id=?']
[Native code: 1146]
[Native message: Table 'roundcube123.accounts' doesn't exist]
[06-May-2010 12:11:26 +0000]: DB Error: _doQuery: [Error message: Could not execute statement]
[Last executed query: PREPARE mdb2_statement_mysql_3167cd130d31ebbb2b10d8729ef25ff76d8c98ba2 FROM 'SELECT * FROM accounts WHERE user_id=?']
[Native code: 1146]
[Native message: Table 'roundcube123.accounts' doesn't exist]
in /mounted-storage/home49b/sub002/sc29675-EMTT/www/webmail/program/include/rcube_mdb2.php on line 269 (GET /webmail/?_task=mail)