This Bosnian grammar looks rather like the cases I deal with in Slovak, so here's how I understand it: s mene = from me sa mnom = with me (sa instead of s just makes it easier to say with mnom)

Sa mnom , sa vama , sa njime , sa njom( e) sa vama , sa nama , sa njima . Means with someone . s mene / tebe it can not be ! It's like with myself or with yourself . Could you help me with Swedish ?

Because as you know B/C/S has 7 cases "sa mnom" - "s(a)" is a preposition and means "with" and is followed by the INSTRUMENTAL case -- with me, with you .. ... "s mene" - "s(a)" is also a preposition and means "from, off" and is followed by the GENITIV case -- from the sky.... Here are some good explanations: http://www.lztranslation.com/serbian_grammar.html