I've had similar problems when importing from blender. I am not too familiar with rhino, but make sure that your normals are all facing outward (sometimes causes problems when importing large blender obj's), you aren't adding lights or cameras to the obj file (again I have had that be a cause in large/complex files), and lastly7 just make sure your obj is poly optimized. Sorry if this is redundant to things you've tried already. Post the obj here and we can try to figure out what is going on with it. Also, post your system/gpu specs if you could.
System 1: EVGA gtx470 1280Mb and MSI gtx470 1280 in Cubix Xpander for Octane, AMD 945, 4Gb Ram
All systems are at stock speeds and settings.