Humm , One of the reasons I like Carrara is it will handle so many characters at once. My lightwaved could not handle more than 7 or so but I've imported over 20 into Carrara many times.  That was with Carrara 3 and amd xp2800's 1gig ram. When I got C5pro I upgraded all my computers to pentium 4's  3.4ghz dual cores still only one gig ram.  As when I tested preformance  with 2 gig of ram it only added 1.2seconds speed on a 30 minute render and no difference on handling scenes. so it was unjustified to add the extra ram.

 The only freeze Issue I ever had was caused by my video drivers on a ati 9600 256ddr card . I could not use textured preview until I removed the catalyst drivers. amd 4000 cpu is 64 bit. my guess is its in that area. As nvidia 64bit drivers are used ? Carrara's not 64 bit , I read somewhere once it cant take extra advantage of 64 bit systems.  with one vicky 3 textured at 3000x on my system carrara uses about 460meg ram. But whats interesting is with 8 it only less than doubles at 760megs used. my page file is set to 5gig so after about 10 vickys it goes into page file but handles them up to about 22 before its slowwwwwwwww.

I would write Eovia and give your system specs and problem.