Before I begin, I must confess that I am fairly new to DotNetNuke (about 2 months) and I have very little knowledge of the underlying DNN system and the systems upon which it is built. I am a Windows Server 2003 Administrator level user with curiousity in DNN Host level operations.
To restate, I found that I get the "My Posts" error (ORDER BY items must appear in the select list if SELECT DISTINCT is specified. 0) with DotNetNuke 4.3.3 with its Forum Module 3.20.08, included by default in the 4.3.3 Install Package. But when I deleted Forum Module 3.20.08 and installed Forum Module 3.20.06 instead of 3.20.08, the "My Posts" error goes away; "My Posts" works OK.
Here is what I did to remove the most recent version of the Forum Module (at the moment: 3.20.08) and replace it with the last stable release of the Forum Module, 3.20.06 - available (at the moment) from Downloads > Module :: Forum > Download ...
Login to your core portal as Host
(select) Host > Module Definitions
(click the left-hand pencil/edit icon for) Forum
(under the Premium checkbox, click) Delete
(back at) Host > Module Definitions
(click the link for) Upload New Module
(browse to) Forum_3.20.06_Install.zip
Proceed, and the 3.20.06 Forum Module should install OK into DNN 4.3.3 release.
I do not know whether it is a good idea to use DNN 4.3.3 with Forum Module 3.20.06 or not. I did not fully deploy this installation once I tested it. I simply can state that I found the 3.20.06 Forum Module did NOT have the "My Posts" error when working with 4.3.3 DNN for my installation.
I have not yet done a Forum Module upgrade, so I'm not sure what that process is like, or how prone to failure or success it may be. It would great (in this thread) to hear from someone who has done Forum Module upgrades,and/or from someone who can confirm that using DNN 4.3.3 and Forum Module 3.20.06 should be OK to go, until later we can make a Forum Module upgrade to a later release than 3.20.08 (that would not have the "My Posts" error).