Move item to Sent Items folder (outlook 2007)

Hi,

I'm not sure if anyone has encountered this problem before.
Basically, I'm creating a new add-in for outlook 2007.  What I did was
create a new post item and moved it to the 'sent items' folder.
However, when I open this item in the sent items folder and I close
it.. it keeps asking me whether or not I want to save the message
because the properties have changed.  The funny thing is if I close
outlook and I restart it, and then I open the same item again and
close it... I don't get that message anymore.  I was wondering if
anyone out there could help me..

thanks,