I"m not sure if its too late, but the problem is that, you cannot set the columns in design mode if you are binding at runtime. So if you are binding at runtime, go ahead and remove the columns from the design mode and do it pragmatically
ex..
if (dt.Rows.Count > 0)
{
dataGridViewProjects.DataSource = dt;
dataGridViewProjects.Columns["Title"].Width = 300;
dataGridViewProjects.Columns["ID"].Visible = false;
}