Crashing on large model, exporting, exploding.

[helsinki98]

I am using sketchup 8 pro. I am working on a large model of an area. (61mb) When ever I try and remove groups after a certain stage sketchup will crash, When trying to export an overhead view as a autocad file sketchup will also crash. Im currently trying to remove all materials of the model (with smustard) and it looks like sketchup is going to crash again. I've just upgraded today from a q6600 + 4gb ddr2 to a i5 2500k and 8gb ddr3 and I have had no improvement. Can anyone recommend anything fixes?

Cheers