The body of plain text emails is blank

Two weeks ago, emails from one of our customers started having problems.

First, attachments would not show up in email messages, either in Outlook 2007 or OWA. I traced the problem to "malformed MIME content" (http://support.microsoft.com/kb/961940/en-us) and implemented a workaround (http://social.technet.microsoft.com/Forums/en-US/exchangesvrclients/thread/5ee6b1d2-865f-4c81-bb3e-b72d30d1845f) that entails creating a new Hub Transport Rule. This appeared to solve the problem of missing attachments.

Then last week, emails without attachments from this same customer now have nothing in the body of the email. The body is blank both in Outlook 2007 and OWA, and this is true for at least two recipients.

I looked at the headers of old emails that had no attachments (these emails came in fine), and compared the headers of new emails that had no attachments (these emails have blank bodies), and there are some large differences. Notice the "Content-Type." (See below)

 Old-no-attachment-email---edited.txt New-no-attachment-email---edited.txt

I suspect the customer has "upgraded" their email system and it is not working correctly, since we have changed nothing on our end. I am running Exchange 2007 SP1, and I won't be able to update to SP3 until at least this weekend.

Is there a short-term workaround or fix for this problem? Will updating to SP3 fix the problem?