Try forwarding the "blank" messages to yourselves or another email account and look for any formatting errors or differences. Outlook2003 must insert some tags that RC renders white or somesuch. Then try to replicate any tags or differences you see by sending them from another email client (Not Outlook2003) and verifying RC doesn't show them.
Once that is confirmed, Thomas can determine the fix, and make you happy!
Happy New Year to the list,
-- Robi