Hi,
What version of mojoPortal are you running? I assume you are an admin on the site so it is odd that you would get the error about not having edit permission.
The error about the 404notfound.aspx file not being found can be remedied by finding the "404notfound.aspx" string in the web.config and replacing it with "PageNotFound.aspx". This error doesn't really have anything to do with the problem you're having but it would good to fix so it doesn't clutter the log.
Thanks,
Joe