Broken PDFs when opened in Acrobat when using egstate

I'm getting some really annoying behaviour and I'm hoping someone can 
work it out for me.

(using cpan://A/AR/AREIBENS/PDF-API2-0.69.tar.gz)

I want to overlay an almost-transparent number in a number of places on 
each page. I'm doing it using the following code:

	my $TRANSPARENT = $pdf->egstate; # Called just once
	$TRANSPARENT->transparency(0.9);

	...

	$text->save;
	$text->egstate( $TRANSPARENT );
	$text->font( $FONT_NUMBERS_FACE, $FONT_NUMBERS_SIZE );
	$text->fillcolor( 'black' );
	$text->translate( $PAGE_WIDTH - $right_margin, 0 );
	$text->text_right( $photo_number );
	$text->fill;
	$text->restore;

However:
* in kpdf, that is causing all subsequent text on that page to still use 
the egstate -- as if the restore wasn't there.
* in Acrobat 8, that doesn't cause transparency at all, just a light 
grey that sits on top of everything.
http://rick.measham.id.au/paste/whacked.pdf

If I take out the egstate line, then it works just fine in both (but of 
course isn't transparent)
http://rick.measham.id.au/paste/fine.pdf

If I change all references to $gfx rather than $text, then it works just 
fine in kpdf, but Acrobat complains that the PDF has errors and I need 
to talk to whoever gave me the PDF.
http://rick.measham.id.au/paste/broken.pdf

Is there an option that I've missed that will let me set the numbers to 
almost-transparent that works in all (or at least Adobe's) PDF readers?

Cheers!
Rick Measham