CS3 PDF's read as corrupt on PC

We are a cross platform Mac/PC environment. Just recently upgraded the Macs to
CS3. Completely patched up with updates as recently as last week.
Windows users, on a intermittent basis, cannot open pdfs created on Macs. If I
have another user create the pdf, it will then work even though the Mac user is
creating the pdf from the same source (Quark, InDesign, Illustrator, etc.) file.
This happens internally and just recently with an external PC.
Network info:
Mac
10.4.11
Quark, Adobe CS3
Intels & G5s
PC
Windows XP SP2
Patches up to date as of this morning (WSUS server)
Adobe Reader 7.0 and/or Full Acrobat 7.0
Dell Computers

Any help would be appreciated.

Time to test out the transfer method - PDFs can get corrupted is handled 
incorrectly over email as an example.

You might want to use a USB disk over sneakernet (walking) from one 
machine to the other   ;-)