Goto http://www.caiway.nl/ Click on one of the buttons (SHOP, INTERNET,RTV,VOICE etc) at the top of the page. The window will not update automatically after the second click. You can force the window to update by either clicking or resizing the window.
The symptoms here look identical to those on bug 4477. The horizontal frame resize bar appears briefly when clicking on the blank page, just before the content appears.
Can't reproduce in TOT, assuming the fix for bug 5768 fixed this. *** This bug has been marked as a duplicate of 5768 ***