Steps for reproducing was supplied by the client.
1. Login to the admin->security->general and enable "allow anonymous access". (To ensure that anonymous access is allowed)
2. admin->security->crowd integration enable and set session validation interval to smaller number so that an active session gets validated on crowd.(I set this to 1 minute)
3. login to crowd and invalidate the user session that you have logged in from artifactory. (Note the browser still has the session as valid for crowd.token)
4. after about 5 minutes(I have set it at 1 monute as per step 2) or visit one of the repository url directly eg: https://<DOMAIN.COM>/repository/test_repo (This will contain empty listing and the error you will see on the logs are as below)
2014-12-02 13:03:36,587 [ajp-bio-8019-exec-6] [INFO ] (o.a.a.s.a.c.CrowdSsoAuthenticationFilter:75) - Unable to authenticate Crowd SSO request: Failed to find entity of type [com.atlassian.crowd.model.token.Token] with identifier [MG7Dwwg7OHamDrGjgpZgPw00]