there should be something that looks like this in one of you rc files

RainmeterIniFile "$ConfigDir$rainmeter.ini"
RainmeterSkinPath "$ConfigDir$rainmeter-skins\"


it's probably in theme.rc but not necessarily.

i would assume that seeing as the path points to a directory outside of the theme folder the theme author hasn't included a skin so just comment that line out and see what happens