Just for interest
Got it solved. The file size gets over 2MB and when you do a paperspace, well TC battle a bit after all the "paperspace" works is done with the goiing "orange" screen and all the zig zag lines on screen that forces you to extent zoom to get it right again in workable manner. If you try and do a Hidden Line render in such conditions, the TC render engine looks like do not wanna cope - it is a 3.0GHZ machine, 4GB 1.333MHz DDR 3 Ram, was a GTX 8800 card and now a GTX 295 card. Thus power, there is enough of, it is a TC thing.
Thus - go out of TC, restart and there it is. All rendering OK.
Really hope they work on multi CPU & GPU system. That is the base of developments now. Cad's with those features will have a ball and user's on other CAD's also squeals for it and two of them that we use, with the new 2010 releases does use it ( But we have not bought it yet )
Come on TC - you can do it - TC 16 is a good, good product - just that extra mile - al computers are at least multi-core now.