Steps to reproduce:
1) Launch OpenOffice 
2) Click on File - New - Presentation
3) Presentation wizard pops up.
4) Select Empty presentation and click next
5) In screen 2 of the wizard and click next
6) Choose any effect in screen 3

Patch fixes the crash - although, I'm still not getting a nice preview of the
effect for some reason:

--- sd/source/ui/slideshow/slideshowimpl.cxx	28 Jan 2005 15:53:08 -0000	1.9
+++ sd/source/ui/slideshow/slideshowimpl.cxx	25 Feb 2005 15:38:47 -0000
@@ -455,10 +455,13 @@ bool SlideshowImpl::startPreview( 
 			mpView->AddWin( mpShowWindow );
 
 		// call resize handler
-		const Rectangle& aContentRect =
mpViewShell->GetViewShellBase().getClientRectangle();
-		maPresSize = aContentRect.GetSize();
-		mpShowWindow->SetPosPixel( aContentRect.TopLeft() );
-		resize( maPresSize );
+		if (mpViewShell)
+		{
+			const Rectangle& aContentRect =
mpViewShell->GetViewShellBase().getClientRectangle();
+			maPresSize = aContentRect.GetSize();
+			mpShowWindow->SetPosPixel( aContentRect.TopLeft() );
+			resize( maPresSize );
+		}
 
 		sal_Int32 nPropertyCount = 1;
 		if( mxPreviewAnimationNode.is() )

stack trace (obviously):

#0  0x43e69720 in SfxShell::GetViewShell () from ./libsfx680li.so
#1  0x466801cf in sd::ViewShell::GetViewShellBase () from ./libsd680li.so
#2  0x469443ff in sd::SlideshowImpl::startPreview () from ./libsd680li.so
#3  0x4693fa7c in sd::Slideshow::startPreview () from ./libsd680li.so
#4  0x4679037f in SdDocPreviewWin::startPreview () from ./libsd680li.so
#5  0x46b178ae in AssistentDlgImpl::EffectPreviewHdl () from ./libsdui680li.so
#6  0x46b177f2 in AssistentDlgImpl::LinkStubEffectPreviewHdl () from
./libsdui680li.so
#7  0x40171d65 in Timer::Timeout () at gen.hxx:127
#8  0x40171a69 in ImplTimerCallbackProc () at gen.hxx:127