I think you're on to something with the predraw.  I tried inserting blank
slides and I'm still having the same issues.  As I said my game is kind of
like a maze so there are times when the player must revisit slides previously
viewed.  This is where my shapes seem to disappear, upon revisiting slides
previously viewed.  They will come back however if I view a slide I've not
viewed yet and even when I revisit a slide for the 3rd time.  Is there a way
to make ppt think that it's viewing each slide for the first time?

Getting better, but still the same problem.  I've tried everything
recommended.  Some work, but not perfect.  Some do not.  I've put a blank
slide between all my slides.  That has helped, but it's not perfect.  My
pictures will still hide on some slides and then reappear.  Also, sometimes
they don't reappear.  I'm starting to wonder if this is because of my game
design and how the player advances from slide to slide.  As I said it is kind
of like a maze.  From slide one the player can go in 4 directions (this is
just an example, not exact: right - slides 2 - 11, down - slides 12 - 20,
left - slides 21 - 30, and up - slides 31 - 40.  The objective is to find the
shapes but in the correct order (lets say the order is star, oval, triangle,
and then heart.  So lets say the player chooses to go right where they find
the triangle.  Since the triangle is not the first shape in the order they
must go back each slide until they reach slide 1 (this game is also about
remembering where everything is, thus the reason to go back).  They've
reached slide 1 and decide to go up where they find the star.  They click on
the star and it appears in the box displaying the shapes found and they are
told what shape they have to find next. The inactive oval on slide 10 hides
and the active (the one that runs the macro for the next shape) now appears.  
From here they have to go back to slide 1 and hopefully they've remembered
which direction to take to get back to the oval.  

So you see it's possible they can go in 3 wrong directions before finally
finding the correct shape.  Could this back and forth movement be the cause
of my problem (i.e., revisiting slides previously viewed)?

Here's my code for hiding the shapes.  Note I'm not actually using the
shapes mentioned above.  This code works well for hiding my shapes.  Doesn't
seem to be any problems here.
Sub HideMe2()
Dim oSld As Slide
On Error Resume Next

For Each oSld In ActivePresentation.Slides
 oSld.Shapes("walletMaster").Visible = msoFalse
 oSld.Shapes("moneyMaster").Visible = msoFalse
 oSld.Shapes("bananaMaster").Visible = msoFalse
 oSld.Shapes("bucketMaster").Visible = msoFalse
 oSld.Shapes("cupMaster").Visible = msoFalse
 oSld.Shapes("eggMaster").Visible = msoFalse
 oSld.Shapes("keyMaster").Visible = msoFalse
 oSld.Shapes("keyhole2").Visible = msoFalse
 oSld.Shapes("moneyFarm2").Visible = msoFalse
 oSld.Shapes("bananaStore2").Visible = msoFalse
 oSld.Shapes("bucketMountain2").Visible = msoFalse
 oSld.Shapes("cupLake2").Visible = msoFalse
 oSld.Shapes("eggDesert2").Visible = msoFalse
 oSld.Shapes("keyJungle2").Visible = msoFalse
 Next

On Error GoTo 0
End Sub

Here's my code for making them reappear along with a couple of explanations
of how things work.  This is where I seem to be having problems.

Clicking on the wallet picture runs this procedure.
Sub WaterFall()
Dim oSld As Slide
On Error Resume Next
'Finding the wallet is the first picture they must find.  
'When they find and click on it picture moneyFarm hides and
'picture moneyFarm2 becomes visible.  
For Each oSld In ActivePresentation.Slides
 oSld.Shapes("walletMaster").Visible = msoTrue
 oSld.Shapes("moneyFarm2").Visible = msoTrue
 oSld.Shapes("moneyFarm").Visible = msoFalse
 Next

On Error GoTo 0
End Sub

Picture moneyFarm2 runs this procedure.  This is the second picture they
must find.
Sub Farm()
Dim oSld As Slide
On Error Resume Next

For Each oSld In ActivePresentation.Slides
 oSld.Shapes("bananaStore2").Visible = msoTrue
 oSld.Shapes("moneyMaster").Visible = msoTrue
 oSld.Shapes("bananaStore").Visible = msoFalse
 Next

On Error GoTo 0
End Sub
Sub Store()
Dim oSld As Slide
On Error Resume Next

Clicking on the bananaStore2 picture runs this procedure.
For Each oSld In ActivePresentation.Slides
 oSld.Shapes("bananaMaster").Visible = msoTrue
 oSld.Shapes("bucketMountain2").Visible = msoTrue
 oSld.Shapes("bucketMountain").Visible = msoFalse
 Next

On Error GoTo 0
End Sub

bucketMountain2 runs this.
Sub Mountain()
Dim oSld As Slide
On Error Resume Next

For Each oSld In ActivePresentation.Slides
 oSld.Shapes("bucketMaster").Visible = msoTrue
 oSld.Shapes("cupLake2").Visible = msoTrue
 oSld.Shapes("cupLake").Visible = msoFalse
 Next

On Error GoTo 0
End Sub
Sub Lake()
Dim oSld As Slide
On Error Resume Next

cupLake2 runs this.
For Each oSld In ActivePresentation.Slides
 oSld.Shapes("cupMaster").Visible = msoTrue
 oSld.Shapes("eggDesert2").Visible = msoTrue
 oSld.Shapes("eggDesert").Visible = msoFalse
 Next

On Error GoTo 0
End Sub

eggDesert2 runs this.
Sub Desert()
Dim oSld As Slide
On Error Resume Next

For Each oSld In ActivePresentation.Slides
 oSld.Shapes("eggMaster").Visible = msoTrue
 oSld.Shapes("keyJungle2").Visible = msoTrue
 oSld.Shapes("keyJungle").Visible = msoFalse
 Next

On Error GoTo 0
End Sub

keyJungle2 runs this.
Sub Jungle()
Dim oSld As Slide
On Error Resume Next

For Each oSld In ActivePresentation.Slides
 oSld.Shapes("keyMaster").Visible = msoTrue
 oSld.Shapes("keyhole2").Visible = msoTrue
 oSld.Shapes("keyhole").Visible = msoFalse
 Next

On Error GoTo 0
End Sub

Thanks,

Mike