When bug 4832 was fixed, a bug was introduced which makes the authentication fail if the system is somewhat busy. It's a race condition between the tlwebaccess process and the pamtester helper binary.
I believe I've managed to fix this in 28132. Keeping bug open until next nighty build, which will be installed on demo systems and possible published as hotfix.
Extensive testing is required. In addition to all test cases mentioned on bug 4832
and bug 4132, we also need to test on a loaded system. This bug was discovered while running /opt/demosyst/libexec/setquotas.py on eudemo, so that might be a good test case.
Hotfix uploaded to http://www.cendio.com/downloads/updates/b4895/. Also installed on both demo servers.
Tested using build 4289:
Created a script to create a heavy load (disk i/o, tty i/o and cpu) on a virtual machine. Couldn't reproduce the problem. All test logins got authenticated correctly. 10 seconds from hitting the login button to get to the actual desktop.