I think this is an issue best handled by your official Jive support channel: check out http://community.jivesoftware.com/support.jspa
Jive 4.5 is a bit older, so I'm not sure that many of us would be able to try and replicate the issue on our own communities, but it also sounds like you're dealing with a little bit of a large ecosystem than just a single community instance.
For example: I am not familiar with a platform called "BlogPost" and I'm not sure how you integrate with it. Your logs may be clean on the source (community) side, but have something on the destination end.
I have not heard of this particular issue before. Have you tried various length posts, words, with an without urls and html markup?