It sounds like you have a geometry error with one of your slab constructions (possibly along the lines of a self-intersecting shape error or something similar) that's affecting how ArchiCAD calculates the 3D translation of the shape. Or the error might lie with one of any of the other elements that are either intersected or "booleaned" by the offending element.
Either way, if you can't isolate the offending element causing the error ( by hiding everything and regening the 3D window after revealing each one by one) then you might have no choice but to erase and re-draw all the elements that might be causing the problem.
Often times you will find that this kind of error occurs when there's an intesection or interaction between 2 or more elements ( or from the bad shape of asingle element) that results in a geometry shape that ArchiCAD can't correctly or logically translate into 3D. If you know what it is then there usually are solutions and work--arounds.
I'm not sure if that was helpful at all, though.....