"550 Your message does not conform to RFC2822 standard"

In email lingo does anybody out there know what this message means and how to FIX it? I haven't found a FIX yet and I'm beginning to wonder. I use Incredimail as my email client and my ISP is Earthlink. Neither one knows how to help me with this error message.

I have used Google with no luck on a FIX. Apparently there are plenty of others who have had this problem but no FIX has been posted. Whenever I put one or more names in the BCC: field...as a test I usually just use my email address...the message goes immediately into the OUTBOX but isn't sent. It then gives me the popup message "550 Your message does not conform to RFC2822 standard".

I didn't used to get this message...I could forward a joke or message to several people via BCC: and they would go through without a hitch. My settings are correct and I've tried system restore to no avail. I'm using Windows XP SP2.

Thanks in advance for any and all help on this my friends.