i have a a hudge scene (high high poly bus). the normal ram usage would be far beyond 1.80GB…of course i use the dynamic memory limit. all worked well…then suddenly vray ignores the limit and max crashes at 1.90GB…of course. no matter what i do (merge the scene again, make a new render setup etc etc) the dynamic memory limit does not have an effect on the scene any more…i use max 7 and vray 1.47.03
thanks
i have to add that ~1.34GB ram are full when i open the scene.
Look at this thread http://www.chaosgroup.com/forum/phpBB2/viewtopic.php?t=12647
also try the junk cleaner script.
Open the xref windows and type “(gc)” in the maxscript window.
I also do it 1x before and after opening those windows just to be safe.
Normal program usage should only be 700-1000 mb.
Seach these forums for both of these topics.
avoid showing maps in viewport and shaded view to reduce ‘some’ memory..
If you’re using any overly large maps (say 4096+) or many many maps, you may have to reduce the size of them
and yea, the 1.7 limit is reaaaaaly getting old now 
im sick of that windows limit!
I know you can use the 3gb switch, but it would be great if Microsoft could release a patch to remove the limit
thanks for the replies…yes, the 3gb switch…but i try not to use it. caused me several crashes in the past…and the other methods didn´t work :-/ this !“§$!”$$ memory limit. time for 64bit !!!