Locked object in sequence diagram (VS.NET)

I am creating a sequence diagram. One of the objects I have added has gray handles instead of black ones, and I cannot resize its width. How can I correct this? Note that the other objects or actors can be resized freely since their handles are black.

Thanks in advance.


Dear Gilles,

I guess this is because you have selected the Format -> Auto Fit Size option from the popup menu accidentally? Just deselect it and the object will be resizable.