I seem to remember a similar issue in the past with Unity but when I go from PC to mac some numerical values in the (text-based) unity scene I am working with get changed ever so slightly - e.g rotations may be a tiny fraction different. Though there is no real difference - the amounts seem to be tiny, it appears as a change or conflict in SVN/source-control software.
This is probably the result of hardware differences. Floats (floating point) are subject to differences in precision and they are really sort of fuzzy numbers (approximations) so it is actually possibly that they could be calculated and returned slightly differently between different systems.