I've noticed I get a lot of those problems as well.  Then again, if you were to look at my DXDIAG you'd be scratching your head as to how I can even render to begin with.  I basically have an underpaid, scrawny workhorse doing my eeeeevil 3D bidding.

I don't know what is to blame for this, whether the software or the rig, but whenever I run C7 I very frequently get memory leaks, even when I use the classic workarounds (Remove Unused objects/shaders).  1.) Sigh.  2.) Save.  3.)  Close and reopen.

A while back I found a whole bunch of tips for memory improvements and I compiled them in this thread.  And yes, I've tried the 'pause render' since then, and it does work.

And there's a couple other things I've learned over time:

• Only use high-res textures on models that are close to your camera.  I literally just did this on my last upload, and holy freakin' moo-cow did it make a difference.  It also gives a bit of a faux-DoF effect, which I think is kind of cool ;P
• If you have to go to the modeling room, close that window when you're done.  Sounds simple enough, but I've found many instances where I was lagging, and once I handled that point it seemed to work better.
• Use shaders whenever possible.  If there's a texture map on one of the material domains that gives the piece a metallic appearance, I'll usually replace it with a metallic-type procedural shader.  It might seem like a small improvement, but that stuff can add up over time.

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