This Help Desk does not work properly...when a customer asks something to a seller and after that he goes to the HelpDesk tab he does not see his post, and the other problem is that all vendors who has threads are able to see threads of other users...

these problems are due to the store procedure CAT_ThreadGetAll...I changed the following code

DECLARE @sql nvarchar(2000)
SELECT  @sql = 'INSERT INTO #PageIndex (ThreadID) SELECT CAT_Threads.ThreadID' +
  ' FROM CAT_Threads, CAT_Posts (nolock)' +
  ' WHERE (CAT_Posts.PostID = CAT_Threads.LastPostedPostID)' +
  ' AND (CAT_Threads.PortalID = ' + CONVERT(varchar, @PortalID) + ')' +
  ' AND ((CAT_Threads.CategoryID = ' + CONVERT(varchar, @CategoryID) +  ') OR (' + CONVERT(varchar, @CategoryID) + '= -1))' +
  ' AND ((CAT_Threads.NotifiedUserID = ' + CONVERT(varchar, @NotifiedUserID) +  ') OR (' + CONVERT(varchar, @NotifiedUserID) + '= -1))' +
  ' AND ((CAT_Threads.NotifiedUserID = ' + CONVERT(varchar, @CurrentUserID) +  ') OR (' + CONVERT(varchar, @CurrentUserID) + ' in (select CreatedByUser from CAT_Threads inner join CAT_Products on CAT_Threads.CategoryID = CAT_Products.ProductID)) OR (' + CONVERT(varchar, @CurrentUserID) + '= -1)) ' +
  @Filter +' ORDER BY ' + @Sort 

by this

DECLARE @sql nvarchar(2000)
SELECT  @sql = 'INSERT INTO #PageIndex (ThreadID) SELECT CAT_Threads.ThreadID' +
  ' FROM CAT_Threads, CAT_Posts (nolock)' +
  ' WHERE (CAT_Posts.PostID = CAT_Threads.LastPostedPostID)' +
  ' AND (CAT_Threads.PortalID = ' + CONVERT(varchar, @PortalID) + ')' +
  ' AND ((CAT_Threads.CategoryID = ' + CONVERT(varchar, @CategoryID) +  ') OR (' + CONVERT(varchar, @CategoryID) + '= -1))' +
  ' AND ((CAT_Threads.NotifiedUserID = ' + CONVERT(varchar, @NotifiedUserID) +  ') OR (' + CONVERT(varchar, @NotifiedUserID) + '= -1))' +
  ' AND ((CAT_Threads.NotifiedUserID = ' + CONVERT(varchar, @CurrentUserID) +  ') OR ' +
              '(EXISTS (SELECT * FROM CAT_Products WHERE ProductID = CAT_Threads.CategoryID AND CreatedByUser = ' + CONVERT(varchar, @CurrentUserID) + ')) OR ' +
              '(EXISTS (SELECT * FROM CAT_Posts WHERE ThreadID = CAT_Threads.ThreadID AND CreatedByUser = ' + CONVERT(varchar, @CurrentUserID) + ')) OR ' +
              '(' + CONVERT(varchar, @CurrentUserID) + '= -1)) ' +
  @Filter + ' ORDER BY ' + @Sort