Files become corrupted under sp1 - upon dr render an error box pops up ‘the file is possibly corrupt, do you wish to resave?’
re saving saves a corrupt file
and not re saving results in a corrupt file.
it then goes on to render the light cache, which just sits there forever with zero cpu use and has to be ctrl alt deleted. Then its back to an hour old autobak file. 
Which 3ds Max version, what operating system? Also, do you have administrator privileges when using V-Ray?
You can also try to clean up any files named vray_client_scene.max anywhere inside the 3ds Max folder.
Best regards,
Vlado
yeah it does mention vray_client_scene.max
xp64, max 9 64, vray 1.5sp1 64. and i have full admin. (though not actually logged in as admin)
a search of my hard drives shows me that file does not exist ( i have exited max)
In what way is it mentioned?
Best regards,
Vlado
i didnt keep a screen shot of the dialoge box but when i rendered it mentions that the file (vray_client_scene.max) is ‘possibly’ corrupt and do i want to resave?
saying yes gives me a save file dialog which is in the original file name, and if i save it as another name (or the original name) it says the same thing again until i say no, at which point it starts to render but just sits in 0% usage limbo not building a lightcache.
dunno if it helps but i think both times, i hit save and then clicked render before the save had finished, thus render was hit ‘instantly’ automatically by the computer when the save was complete.