My post company is capturing 15:1s over mojo SDI on a MacPro using 10.4.8 and xpress 5.7.5... we are shipping drives across the country to different editors... we started capturing mxf but have been told by one of my editors that he has been receiving footage in omf from other sources... I have been told to start capturing omf... any potential problems during online mixing omf and mxf? Footage is seen, can be edited no probs... just want to flag any potential probs down the line.

No problems whatsoever. I have been mixing both on timelines for over 2 years now.  Let your editors know.  You can continue to capture in MXF.  If and when you go HD or migrate to a tapeless exchange environment using Avid Airspeed, it will be MXF exclusively.

cool... thanx