You can't log into SiteAdmin because your username has a lower case letter at the start. Read this page for more information. It is not enough to simply log in with a capital letter, your username has to start with a capital letter and you need to log in with said capital.
- Follow the instructions in the link to get a new username starting with a capital.
- Log into the forum and make three posts
- Then you should be able to log into the forum, SiteAdmin and the CGWiki all with the same login details.