I have the same problem from the moment when change the licences for mac. I take the latest fully upgraded Imac. Before that I work on a HP Work station and never have this kind of problems. I also sent lot of notifications to vray and sketchup, they contact me, we speak also about this problems and try to solve online thru phone conversation, they can't fix anything.
They must to admit they have a big problem regarding the compatibility between SU&Vray. Soon I upgrated to the SU 2013 and soon I will upgrade the vray also in a hope of a better working, but in the trial versin of Vray I all ready have some crashes.
Any way in the trial version you can't experiment almoast nothing, is a bull shit. I don't understand why are so scared.
Probably the best solution it will be to have everything on Windows system, I loose my patience from two years now.
Few things I experienced already in this two years of using. If once crash, is crash all the time. So open a diferent existing file, and the sketchup will open the new and the crashed file also. You can work on it. Possible in the major file, vray don't show the materials, save it as a diferent file and open it again.
If don't work, open a diferent file of sketchup, unactivate the vray plugin after that you will don't have any problem with the sketchupfile until you activate the plugin back.
The moast crashes is happening because of the materials or memory problems. So close moast of the aplication befor use SU&Vray.