when Scrolling down the page, header remains but content of the table disappears...any fast solution(s)??

Hi...I have sliced a PSD into a Drupal 6 theme...other things are OK(as of yet), but one problem im getting right now.
Suppose i am on the Blocks admin page. as i scroll down to see the rest of the page,
to see the rest of the page, the JS responsible to keep showing the header of the table (Block | Region | Operation) while i scroll down to see the bottom of page, it happens that i see a blank page while i can still see the heading.

What might be wrong??

Regards,
Baloch