Comment 2 for bug 436140

The resizing is not an issue. To clarify, different authentication
options have different numbers and kinds of fields to fill in. For
example, WEP only has a text field and a check box, whereas WPA
enterprise has many sub-options of various types. Furthermore, some of
those sub-options also have their own varying number of sub-options.
In general, some options, when changed, affect the number and type of
other options available, and when these options are changed, the
dialog is resized to fit the new set of options, even if the new set
of options is exactly the same size.

The problem is, however, that in addition to resizing itself, the
dialog also centers itself on the screen, rather than holding its
position. This is inappropriate, at least after the user has moved the
dialog. A possible compromise might be this: if the user has never
moved the dialog box, keep the current behavior. Once the user moves
the dialog box, it never moves itself again.

Also, the "Create a new wireless network" dialog shows the same
behavior. This is easier to test because you don't have to go find
someone else's encrypted network to try it.