Thanks for pointing me to William Wang's workaround post.
William, Thanks, yes it worked for me also.
I have been able to achieve 3 high quality static renderings in a row using 2011.
I could not finish 1 before.
Ok why does this work? I have never had to change a programs affinity before? I'm not that much of a computer expert but here are my observations:
Again, I am using HP Dual Processor Workstation, XP Pro 32bit,(3GB switch), 4GB RAM, Nvidia 1GB Graphics Card. Also multi monitors via Matrox Triple Head Unit, + Space Pilot.
Before trying this workaround I have looked at rendering the same model in 2010 & 2011.
With task manager active it became obvious that 2011 Inventor was hitting my memory a lot harder than 2010.
Each time I rendered I could see the page file get larger, within one or two renders it was up around 2GB then Inventor would crash.
Using this work around, CPU 0 is 100% active & CPU 1 appears to be almost inactive.
However, looking at my page file this time, after 3 renders in a row, the page file is only 1.6GB. & no crashes.
Yes it was slower but it worked.
I've not had the nerve to do any animations yet but from these initial tests,using the workaround, I notice that
after each closing of the render window the page file increases slightly. I assume that the workaround is delaying the inevitable crash which will eventually occur at some point during the animation?
Over to the experts, any clues in the above, hardware or software?