I don't know if this is already known, nothing came up from searches so I'll risk it.
I just made edited myself a theme to use in Dreamweaver on my iMac and the theme chooser page was full of CSS instead of the name, author and other fields. I soon realised the mistake was not mine and it did this to any style.css I saved, even just resaving the CSS doc for the default style without editing it caused the same thing to happen.
The problem seems to be line-break related as far as I can see because cut'n'pasting the contents of style.css into Vim, which obviously uses unix instead of mac line breaks, and saving in that then uploading it again fixed it.
A slightly annoying if trivial problem really. I use 1.5.1 btw.