C#: Windows Forms: What could cause Invalidate() to not redraw?

I'm using Windows Forms. For a long time, pictureBox.Invalidate(); worked to make the screen be redrawn. However, it now doesn't work and I'm not sure why.

this.worldBox = new System.Windows.Forms.PictureBox();
this.worldBox.BackColor = System.Drawing.SystemColors.Control;
this.worldBox.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle;
this.worldBox.Location = new System.Drawing.Point(170, 82);
this.worldBox.Name = "worldBox";
this.worldBox.Size = new System.Drawing.Size(261, 250);
this.worldBox.TabIndex = 0;
this.worldBox.TabStop = false;
this.worldBox.MouseMove += new 
    System.Windows.Forms.MouseEventHandler(this.worldBox_MouseMove);
this.worldBox.MouseDown += new 
    System.Windows.Forms.MouseEventHandler(this.worldBox_MouseDown);
this.worldBox.MouseUp += new 
    System.Windows.Forms.MouseEventHandler(this.worldBox_MouseUp);

Called in my code to draw the world appropriately:

view.DrawWorldBox(worldBox, canvas, gameEngine.GameObjectManager.Controllers, 
    selectedGameObjects, LevelEditorUtils.PREVIEWS);

View.DrawWorldBox:

public void DrawWorldBox(PictureBox worldBox,
    Panel canvas,
    ICollection<IGameObjectController> controllers,
    ICollection<IGameObjectController> selectedGameObjects,
    IDictionary<string, Image> previews)
{
    int left = Math.Abs(worldBox.Location.X);
    int top = Math.Abs(worldBox.Location.Y);
    Rectangle screenRect = new Rectangle(left, top, canvas.Width, 
        canvas.Height);

    IDictionary<float, ICollection<IGameObjectController>> layers = 
        LevelEditorUtils.LayersOfControllers(controllers);
    IOrderedEnumerable<KeyValuePair<float, 
        ICollection<IGameObjectController>>> sortedLayers 
            = from item in layers
              orderby item.Key descending
              select item;

    using (Graphics g = Graphics.FromImage(worldBox.Image)