Thanks for your help.
I learned to disable the automatic line function in the help option in Writer:
To disable the automatic borders, choose Tools - AutoCorrect - Options and clear Apply border.
Also, by locating the cursor at the beginning of the line above the line, selecting FORMAT - PARAGRAPH - BORDERS - and clicking the "set no borders" box and "OK" the linne will be removed.
Thanks for the hints you gave me.
OOo 3.0.X on Ms Windows XP