By the way this is what I did.

First I opened SQL Server Management Studio and went to my dnn database.  If you don't see your db you have to attach it first.  Navigate down into Programmability > Stored Procedures.  Right click on stored procedures and click Modify.  You will see a window on the right side where you can change change the stored procedures.
Look for this line:

@Filter + ' GROUP BY P.ThreadID , P.CreatedDate ORDER BY P.CreatedDate DESC '

Change it to that:

@Filter + ' GROUP BY P.ThreadID , P.CreatedDate ORDER BY P.ThreadID '

That's all I did to fix this problem.  Hopefuly it will solve your problem.  I don't know why this was happening.  I have the most recent version of dnn.  4.3.6