Steps to reproduce are easy:
1. > grails create-app com.my-project
2. > cd com.my-project
3. > grails create-domain-class com.A
4. > grails create-controller com.A
5. Edit com.AController and add the line : "def scaffold = A"
6. > grails run-app
7. Open browser, go to main page and click on the AController link
8. BOUM => HTTP Status 404 with description "The requested resource (/my-project/A/list) is not available."
Actually, if you try the url /my-project/a/list (with a in lower-case) then it works.
Note that if you go to : /my-project/a/create and create an A instance, the redirect page will also return an 404 error.