Okay, so I can't seem to get it right. Here is what I'm working on:
http://dagloos.com/lust/index.php?album=photography/digital/

I'm happy I finally got the masonry javascript working, but all I need to do now is to make all the thumbnails the same width. When I edit the thumb size in my theme options, it just grabs the longest side of the image and resizes it. Please, please help me. It's probably very simple, but my knowledge of PHP isn't that great..

You will have to edit the theme if you wish to do this with uncropped thumbs. Two options:
a) Use the check for landscape images and use image functions to set the size accordingly
b) Use the set of maxspace image functions to define a fixed width x height.

Please search the documentation and the forum about that. Nearly all of our functions are named accordingly so the names gives an idea.

Thanks for the fast response! I did search the documentation and forum, but I just didn't get how to use the code or how to search for what I needed. I now replaced the code with:

Exactly what I needed. Thank you very much for clearing it up for me!

Glad you got it. Always welcome!