Email displaying squares instead of text

[glenforum]

ok, here goes.... win 7 64-bit, Office 2010 SP1 - 32 bit, Exchange server 2007.

We are getting several emails with empty squares in the message body instead of text. (but not all of the text.)



odd thing is, if I switch Outlook to read emails in plain text mode, some of the emails display all of the text just fine.
On other emails, the squares turn into smaller boxes with a question mark inside.

multiple machines, with multiple user accounts