need urgent help....

My 3ds max file closes when i render the scene..I use 3ds max design 2010, solidrocks, multiscatter for trees..All trees are proxies.. trees are not much..
In solidrocks i am using default method..while computing lightcache the calculation stops for a second and file closes..
want to know what is the problem...before i didn't had any problems..from past 2 weeks i am facing this problem. i even tried changes the antilaising filters...but no use...
best part is after several attempts of rendering and closing the file..finally it rendered...but again once i restart the computer and open the file again same problem it won't render the file closes.. I GUESS MIGHT BE RAM PROBLEM OR SOMETHING ELSE...please help me in this issues. will be very glad and thankful..

3ds max design 2010
vray 1.5 sp5
solidrocks
multiscatter
windows xp 64 bit
6 GB ram

does no one knows whats the problem...!!!!