Deby create LOCK on my table and do not release it , what is my mistake ?

[Legolas Woodland]

Hi
Thank you for reading my post.
I have an update statement which i execute over a table in my database.
now when i execute the update statement from my application (even after 
i exit the method that update the table)
i can not use select statement over the same table.
here is my update statement:

   String sql = "insert into FILTERED_BANNER(BANNERBANNERID, 
WEBSITESWEBSITEID) values ("+extractBannerID("Test")+","+     
getDropDown1().getSelected().toString()+")" ;
      st.executeUpdate(sql)
     con.commit();
     con.close();


st and  con  are defined in constructor , connection  is not auto 
commit. , and con come from a datasource.


here is the derby message after execution of select statement :

select * from FILTERED_BANNER;

and derby says :
org.apache.derby.client.am.SqlException: A lock could not be obtained 
within the time requested