I had an interesting time figuring out why my gallery was no longer visible after I installed your plug-in, and as it turns out it was my CSS framework.
In many frameworks the css class "clear" is defined as
clear:both; display:block; overflow:hidden; visibility:hidden; width:0; height:0;
The <div class="clear"></div> is a common methodology used throughout many CSS frameworks so I thought perhaps you could consider removing the class "clear" from the gallery-row DIV, or at the least, put it in after each <div class="gallery-row"> - that way it will clear each DIV without obstructing the visual. This is just my little input - perhaps this will make this plug-in more accessible.
For now I simply removed the "clear" class from the .php file in your plug-in.. however, at the moment, as soon as my customer updates the plug-in automatically, the gallery will once again become invisible until I tinker with the code. I guess I could put an override code in my css stylesheet for now so that the .clear class under .gallery are forced to be visible.
Great plug-in by the way - enjoying it otherwise.