I enterred a strange problem. I solved it, but I thought to place it here incase...
In the users table I created a column ID (+ auto_increment) and by mistake I clicked on primary key! I did not check if there was one defined. There were TWO of them defined, as I could see in the phpMyadmin. Some things were not working.
I did resnyc the def files. That created even worse. Because in the 'ai' => '', it was what should not have been!!! Try it out.
Many times I tried to resync, but no change. I discovered only when I manually checked what the resync was doing. By this time I had tried a lot.
I need an incremental ID in the table Users. I do not want Primary key as users.
What I do not know is if at all the scripts are using this primary key Username for some reason. Would it be safe to delete this key and use ID instead? Instead of having anathor problem, I thought of asking. (I did not check the searches, BTW, if this had been discussed.)