1. Go to [Manage Jenkins]->[Configure System], then select [Jenkins's own user database] and [Project-based Matrix Authorization Strategy].

2. Add an existing user using the 'User/group to add' input box; pressing add to submit

Observed Behavior
In the security matrix grid, the user name displays briefly in column "User/group".
After a fast refresh, the username is replaced by 'Error' link.
Navigating to link displays 404 in cell:

Status Code: 404

Exception:
Stacktrace:
(none)

Generated by Winstone Servlet Engine v0.9.10 at Sat Apr 16 23:53:00 PDT 2011