After debbuging a while, I found that the Uniform module search for css Themes in
/sites/all/libraries/uniform
When documentations says to copy / paste Uniform files (downloaded from http://pixelmatrixdesign.com/uniform/) in Libraries.
Please understand that you should not (like I did first) copy / paste those files in /modules/libraries/uniform, but you have to create the libraries folder in /sites/all and then paste the files there.
TO DO : please update the installation section of the README file to clarify this point.
Comments
Comment #1
realityloop commentedresolved in 6.x-1.1