Filmstrip view window in XP too small- can’t adjust?

This is an odd one. Somehow, the lower section of the filmstrip view (XP Pro) has been adjusted down so that you can only view about half of the photo thumbnail- it now has a tiny scroll bar to the right. The whole image appears in the upper part of the window just fine, when selected- but it’s a pain that I can no longer view the entire thumbnails below.
If I hover the mouse between the two panes, I do get the double arrow- as if I can adjust it- but it won’t do anything when I try to drag it upwards…I’ve Googled my tail off and see nothing related to this.

Here’s a screenshot:

http://i3.tinypic.com/2ykxi4k.jpg

Help?
Tracy