[TYPO3-project-seminars] sql error, speakers not editable in list view in backend

[Ben Kerner]

hi group,

if i select the speakers-sysfolder in the typo3 backend with the list view, 
a sql error appears:

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result 
resource in /opt/lampp/htdocs/website/t3lib/class.t3lib_db.php on line 796

The speakers aren´t visible in the list. if i try to create a new 
speaker-entry and enter a name and save: another error appears:  2: SQL 
error: '' ()

In the Seminars-view i can see the speakers, but if i try to delete one, a 
sql error appears:

100: You have an error in your SQL syntax; check the manual that corresponds 
to your MySQL server version for the right syntax to use near 'ORDER BY 
title='1000000000' WHERE uid=7' at line 5

how can i debug the sql-queries to find out whats wrong?

greetings
ben