dont know since this still remains a unique one off occurrence… there is one change to the unread post list that will be in 5.1 but since we cannot duplicate it, dont know if it will help your situation or not… 5.1 is slated to release on the 31st of May…
other than that, I am not sure where Andy is on his research of this one… Is is gone for most of today, so probably tomorrow before he gets back on this…