Installed manually (i.e., just copied the folder into the skins directory). But it's weird, since everything else works.
I'll try to use your installer.
And by "plugin" in my last post I obviously meant "skin"... and also "0.5" instead of "5.0".
I'm using Roundcube 0.4 and thinking about switching to the next version, but from 0.3 to 0.4 a lot of themes just didn't work for quite a while, so I want to make sure everything works and I don't need to "downgrade" afterwards. Can't stand the default skin, I hope they bring forward the skin redesign to an earlier milestone than 0.7.