Strange IE behaviour with float:left ...

 Hi,

I am trying to develop a picture browser, and therefore have a thumbnail 
page as a starting point.

With help, I got the float:left statement to do just what I needed, but it 
doesn't seem to always work in IE...

To see the behaviour, please open this page, and resize it, and scroll down 
the right DIV...

http://ruipaiva.dnip.net/pbnew/PictureLibrary.html

As you can see, some of the spaces where there should be a thumbnail are 
empty... I have no idea why, and as I said, it works fine in Firefox...

Any ideas ?

Thanks .

Rui