Lyne - I don't believe your problem is the video card(although Nvidia does appear to work better with ALL 3d apps)  Everything is very slow in V6 now(the latest update). This last update is totally fubared - roll back.  A lot of people are having the same problem, also check over at at EON forums, various threads on this same issue :) I have 4G of ram & still crashing like a banchee(newest update).

See this thread as well:

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2683338