I got memory crashes too. Playing on 32 bit with 2gig sooo...
I installed a memory cleaner wich is automatically run when the system ram runs low.
As we know M&B precaches all textures if you chose to. You can start a round faster but it also fills your RAM very quick.
Once I got my client down to 800MB use in crpg, lucky shot though.
If you do use a memory cleaner in the background, do it when youre dead, because you cant really play when the cleaner throws out all textures and M&B tries to reload them again.
This method works for me, sometimes I manage to leave M&B on in game for hours without memory crashes.
The only solution to cut this down is to use the same resources for building maps (not to many different props) and reduce the size of the textures/meshes. Optimization is the big deal here.
I'm not sure but most of the native gear doesn't even have specular and bump - maps. Some new texture packs textures are as 3 times as big as the native ones. We need some eyecandy yes.
I favour specular maps over bump maps. So please whenever a new texture is made try to keep files at a minimum sizes where it still looks nice, and not the maximum noone will notice in the heat of battle.