SetArtUserAttr(art, kArtHidden, 0); not working in CS4

I have a CS3 plug-in that I have converted to CS4. Part of the process is that I hide text objects and save layers as PDF files. At the end of the process I want to show all the objects that I have hidden so that I can save as an Illustrator CS2 file for archiving. To do this I execute the following code by calling ShowAllArt(); below. The call to SetArtUserAttr works fine in CS3 so when I save as an Illustrator CS2 file and re-open the save file, all objects are visible. When I do the same in CS4, SetArtUserAttr returns kNoErr but on opening the Illustrator CS2 file, the text objects are still invisible in the layers palette. Is there something I should do in CS4 before I save (like sAIUtils->AppIdle();) ?

static void ShowAllArt (AIArtHandle inArt)

{

if (inArt)

{

sAIArt->SetArtUserAttr (inArt, kArtHidden, 0);

short type;

if (!sAIArt->GetArtType (inArt, &type))

{

if (type == kGroupArt)

{

AIArtHandle child;

if (!sAIArt->GetArtFirstChild (inArt, &child))

{

while (child)

{

ShowAllArt (child);

if (sAIArt->GetArtSibling (child, &child))

break;

}

}

}

}

}

}

static void ShowAllArt ()

{

AILayerHandle theLayer;

long count;

ReturnIfError (sLayer->CountLayers (&count));

for (long i = 0; i < count; ++i)

{

if (!sLayer->GetNthLayer (i, &theLayer))

{

if (theLayer)

{

sLayer->SetLayerVisible (theLayer, true);

sLayer->SetLayerIsTemplate (theLayer, false);

AIArtHandle art;

if (sAIArt->GetFirstArtOfLayer (theLayer, &art))

return;

while (art)

{

ShowAllArt (art);

ReturnIfError (sAIArt->GetArtSibling (art, &art));

}

}

}

}

}