The object cannot be deleted because it was not found in the ObjectStateManager

The problem is you cannot delete (or remove) detached entities and cannot attach an entity twice. You need something like below.

var entry = db.Entry(myCurrent);
if (entry.State == EntityState.Detached)
    db.myTable.Attach(myCurrent);
db.myTable.Remove(myCurrent);

The other answer didn't work, so here's how I fixed it.

Previously I had:

public void ok(myTable myCurrent)
{
    //delete entries from other tables in relationship with myTable
    db.myTables.DeleteObject(myCurrent);

}

I fixed it with this:

public void ok(int current_id)
{
    //delete entries from other tables in relationship with myTable
    var y = (from x in db.myTables where x.id == current_id select x).First();
    db.myTables.DeleteObject(y);

}

if you just received model from edit or delete view by post or generated it yourself then EF doesn't know about it so you set its state to "Deleted" (or EntityState.Modified etc) to inform EF by:

//generate it yourself if not posted from edit/delete view
//var model = new Model { Id = 123 };

//set to delete
db.Entry(model).State = EntityState.Deleted; // or EntityState.Modified for edit etc.
db.SaveChanges();