i dont think its an css problem. its seems more to be a javascript problem.
i mean its okay that its hidden. unless you click the create button.
and because the visibility value is directly set in the element and not in a css file i think this value is set by javascript
and should also be removed by javascript. And heres the error its doesnt remove this visibility-style or sets it to "visible"
if you remove that style-attribute from the tag manually it works but only once.^^
Workaround: Just click Go after pressing the Create button. A page is created and you can choose the page type in the page editor on the right
In the tab "Behaviour". Its not a pretty workaround but it works until they fixed this bug. :)