In =media-sound/rubyripper-0.6.2-r1, the Preferences setting to "Replace spaces with underscores in filenames" is checked by default. When unchecked, you would expect there to be no transformation of filenames, but in fact this has the inverse effect: if there are underscores in your file-naming scheme, these are converted to spaces! For example, the naming scheme %a - %b/%a_%n_%t produces the path My Band - Their Album/My Band 01 First Song.ext when you would expect My Band - Their Album/My Band_01_First Song.ext I can't say whether that setting is the cause, as it would be moot if it were checked, but it seems a reasonable possibility.
Please report this upstream. This problem is not Gentoo/Linux specific.
