Severe Problems: Sketchup kills Leopard

Hi folks,

The performance is actually not my issue - but the stability.

After a couple of interactions Leopard shows the beach ball. There is no way to force-quit SketchUp only. The only way out is to power the Mac off.
Leopard should never be but is destabilized by SketchUp.
On top of that rebooting doesn't work in 75% of the cases. After login the Machine remains inactive showing the faded out password screen.
When shutting down via the power-off button a re-start is usually immendiately possible, but sometimes it also takes several consecutive shut-downs.

Leopard allows apps to get into an eternal beachball/coma mode that renders the OS useless.

Maybe (subjective impression) this correlates to quick movements with my mighty mouse (at least a feel like that)

BTW: this effect also happend twice in cover-flow mode of iTunes.

Any ideas about that? Or just hoping that 10.5.3 will eliminate that issue.
I can only work properly with Sketchup after booting 10.4. or Fusion/Windows.

MBP, 4GB, Intel, Leopard 10.5.2, Mighty Mouse