Sometimes when you add a new user to your ESXi 4.x installation, you get this error message (click for the full size picture):
Create User: User name or password has an invalid format
Until now, only a few russian pages described the cause:
Without console login (or SSH – see my blog tomorrow), you cannot see the obvious reason for this message:
Your password does not adhere to the ESXi 4.x password policy, which is more strict than the ESX/ESXi 3.x policy.
vm-help.com has a nice page describing the ESXi 4.x password policy, and how to alter it.
–jeroen