Forum is Ok, so I recovered a backup of the old 1.9.1.8 database to this new intallation, and run install again, and it's ok.

The first problem appeared when I load the forum. The error is the for the language file that don't match the english. I update the language file, and go to the table yaf_Registry to change the contents of the language to english, because none of the language files work. Then I notify that some records, in the field BoardID have the number 1, and other have the value NULL.

I updated manually all the records to have the value 1 on BoardID (I have only one board).

Well, the error is another now, and for that I cannot find a solution:

[IndexOutOfRangeException: There is no row at position 0.]
   System.Data.RBTree`1.GetNodeByIndex(Int32 userIndex) +1943315
   System.Data.RBTree`1.get_Item(Int32 index) +17
   System.Data.DataRowCollection.get_Item(Int32 index) +11
   YAF.Classes.Base.ForumPage.InitDB() +434
   YAF.Classes.Base.ForumPage.ForumPage_Init(Object sender, EventArgs e) +76
   System.Web.UI.Control.OnInit(EventArgs e) +99
   System.Web.UI.UserControl.OnInit(EventArgs e) +74
   System.Web.UI.Control.InitRecursive(Control namingContainer) +321
   System.Web.UI.Control.AddedControl(Control control, Int32 index) +221
   System.Web.UI.ControlCollection.Add(Control child) +146
   YAF.Forum.Forum_Load(Object sender, EventArgs e) +925
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   System.Web.UI.Control.LoadRecursive() +47
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1436

Well, I created a new empty database, then restored the backup again. But, the problem, I think, is caused by the wrong usage of the web.config files.

I'm using the recommended-web.config, that is for new installations, instead of v191-upgrade-web.config, that is for my case. I forgotten to change it when trying to upgrade the forum. :oops:

So, problem solved and the forum is running. :-d