To reproduce:
- Set RadStatusStrip SizingGrip property to false.
- When you move the mouse to the right corner its cursor is changed and you can resize.

Workaround:
- Completely remove the element with the following code:
int lastIndex = this.radStatusStrip1.StatusBarElement.Children.Count;  
this.radStatusStrip1.StatusBarElement.Children.RemoveAt(lastIndex - 1);