alignment of second column on index page

hello

I have a problem with the alignment of the second column
on the index page in my pdf document(page 53 on the attached file).
It overlaps the title of the indexpage.
Does anybody know how to fix this problem ?

I use the DocBook XSL Stylesheets V1.64.1 from norman walsh,
xsltproc 1.1.5 and fop 0.20.5.

thank you very much

roger meier


sorry, about my english.... I'm still learning