Crash when I render a big size rendering?? please help!!

[artchung]

I tried to render a scene with SU 6 & Vray for SU. When i tried to set the output size over 2000 width, My SU crashed @ the second pass.(please see the image below) Why? can someone give a little advice to me here. P.S. it renders ok when the size is around 1500 width. So weird!!! Please help!!