To ThumperGT
Just found this thread today. It's been a while. Did you get to the bottom of it?
Here's my experience...
On a Vista system with Windows Mail, I suddenly began getting a number of "blank" emails, except that their size suggested that they were not empty. From, Date, To and Subject all appear normal - it's just the content or message itself that appears void.
The other symptom common to all these emails - if I "Reply" or "Forward", I cannot place the cursor in the message area.
Had not tried conversion to Plain Text within Windows Mail, but I did discover that if I "Saved As" an eml file, then copied the email to an XP system, the messages opened normally when using Outlook Express 6.
So far does this parallel your issue?
If so, some further findings that may be of interest if you haven't already worked it out...
(1) Several people blame antivirus programs, specifically McAfee and Norton. I can't prove them wrong, but I have not been able to find evidence in my Norton logs of these emails being affected. Furthermore, a possible pattern (see point 3) suggests to me that it's not Norton.
(2) What browser do you use? I have seen one forum where someone has emphatically claimed that this and other problems with Windows Mail stem from incompatibility with IE9. (And one suggested workaround is to revert to IE7/IE8.) Once again, I don't have proof. However, I have noticed that ALL cases of "blank" emails that I have received came after I upgraded from IE8 to IE9. Coincidence or cause? I may get around to uninstalling IE9 to see.
(3) Your Apple association is interesting, but for now I am inclined to rank that third as the probable cause in my case. Why? Well the dozen or so not-really-blank emails that I have received have all come from only two sources. The last two such emails, just in the last few days, came from Symantec/Norton Tech Support. ALL PRIOR ONES were from a particular department at Microsoft! OK, maybe MS staff are covertly using Apple equipment? For now, my assumption is that some mail programs or servers produce an email format that is different to 99% of the emails that I receive, and WinMail (possibly when in conjunction with IE9) can't cope.