Problem is menus link to articles and components and login is a modules so do this
1. Go to the module manager, open the login module and give a unique name in the position field. Example: custom1.
2. Create a new article preferably uncategorized. Give it the name of your module.
3. In the body area of the article type {loadposition custom1} and save your article.
4. Create a Menu link to this article in the desired menu. You should select 'Article layout.'
Thats all, your module will now load from the menu link directly.
This has an added advantage of giving you SEO prominance based on the meta info you give for this article.
Cheers
Ian
yws.com.au