If you have the contact us and become a member pages in the site you should be able to link to them without issue. What is the specific error that you are getting? I'm having trouble understanding exactly where and when this is occurring for you and the exact steps you are taking that are giving you this result. There should not be anything that limits what pages you can link to. If you are making these changes in the tree control area of SiteAssist then you will only be able to make a page with a particular name occur once in the site. This page of the wizard is not for crafting links, it is the control of the sites pages and there relationship to one another. If you have any screen shots this might also help so that I can understand a little better what you are experiencing and why.
