I was browsing and I came across this new VMware KB article which could potentially have widespread impact. This is very important, particularly in lab, development and proof of concept environments. The VMware KB article number is 2069041 and it is titled The vCenter Server Appliance 5.5 root account locked out after password expiration.
The root account of the vCenter Server Appliance version 5.5 becomes locked out 90 days after deployment or root account password change. This is due to a design which follows a security best practice of password rotation. In this case, the required password rotation interval is 90 days after which the account will be forcefully locked out if not changed. This is a well described process to prevent a forced lockout as well as unlocking a locked out root account. Approximately 90 days have gone since the release of vSphere 5.5 and this issue will quickly begin surfacing in large numbers where the vCenter Server Appliance 5.5 has been deployed using system defaults.