I was having problems with a theme called Shaken Grid (really nice theme btw) it uses jQuery Masonry to fit posts together. After asking around and testing I heard that people got a wierd fluid design on the site (http://linolino.be) but this was mainly on Windows. The jQuery that came with my WordPress install turned out to be causing issues (only on some systems which is really wierd and hard to find out) and the use-google-libraries plug-in fixed this perfectly. Now I've got extra caching to boot.
I'm using the Dutch language version of WordPress, I'm kind of suspecting that there's a newline character difference in the js libraries in that language distribution as I didn't have the problem with regular English WordPress.
Just wanted to share this with you, maybe helps someone else some day.