Trouble converting powerpoint files with png images to pdf-Can someone help?

Question

Hello all,
In my line of work, I create and modify large sized posters that are created in powerpoint. I would have the files print ready by converting them to pdf. I usually have little to no issues executing this. However, I have been dealing with an issue of converting ppt files with png images. The size of the ppt is typically a 42x56 file. The several ways to convert to pdf produces an error each time. Png images are very useful as they provide much clarity vs jpegs or tiffs. The 3 ways I have tried below are:
A) File>Print>Adobe PDF>High Quality print settings/300dpi results to an error message that says:
     "Windows cannot print due to a problem with the current print setup. Try one of the following:
     *Check the printer by printing a test page from Windows.
     *Make sure the printer is turned on and online.
     *Reinstall the printer driver"
     A blank pdf opens up (Selected to open file after publishing)
B) File>Save as> Change file type as a pdf results in nothing happening. No pdf is produced.
C) Acrobat>Create PDF results to an error message that says: "An unexpected error occured. PDFMaker was unable to produce the Adobe PDF."
Again, this all happens with ppt files with png images. I took out the png images and attempted to convert to pdf, and the pdf is produced! 
Can anyone provide any assistance in creating pdfs with png images or what settings I need to adjust? I am able to covert every other image type (jpeg, tiff, bmp), except for png images.
I am using Microsoft Office 2010 with Adobe Acrobat X on Windows 7 (This happened on Windows XP as well).

Answer 1

>I have a 48 slide presentation that has a small .png image in the "slide
>master" so it will show up on every page.
PowerPoint only has to store one instance of the image even thought it is
displayed on multiple slides. But Acrobat can't do the same, the image has
to be stored for every page that it appears on, so that would explain the
larger file size.
Acrobat is supposed to be able to optimize the storage of common background
images (at least that's the message I see when I do a "Save as..."), but I
have yet to see it to work. Maybe it depends on the application the orginal
file is created in and the PDF conversion method used.
Adding the image into a PDF file later as a watermark instead may be a way
to keep the size down (then it really only does store the object once),
though I believe that watermark images will appear in front of everything
else on the page (not sure if that's a problem for you, it depends on
whether any text or objects in the presentation ever appear in front of the
image).
What are the dimensions and resolution of the image in PowerPoint? You may
be able to go as low as 75 dpi and not notice a difference, it depends on
whether the image contains any areas of high contrast or text.