tables cannot be used in write mode

Hello,

I use OOf 3.1 and MySQL Connector.
I am able to connect, to open tables, to create forms.
But I am not able to open tables or forms in edit mode (that means to 
change or write data).
If I open a form or table, OOf tells me it is in read only mode though I 
did not select "read only".

Additional: the MySQL JDBC driver has exactly the same problem, so I 
guess it is not driver dependant.

Kind regards
Alex Abramidis