I used apache bench to stress test a Drupal site on my linode Debian squeeze 64 bit VPS. The website broke. You could view it but as soon as try to log in, and browser collects cookies, you get white screen of death on all pages.
Restoring backed up database and code did not fix the problem. Restarting Apaching, and rebooting VPS did not solve the problem.
Deleting the entire Virtualmin and Webmin account & associated data in Webmin & Virtualmin, recreating it with new username, and putting back the Drupal website's code & database (restored from the same backups) solved the problem.
Any suggestions about what was happening here?