The installer may prompt “Failed to established connection” after input SQL database information.
Reason can be vary. If your SQL account password is correct, it maybe caused by SQL password policy. The three password policy is selected by default when you create SQL account.
You could also find similiar error message in %TEMP%/vm-sso-javalib.log:
[2013-01-11 10:54:33,640]ERROR 733[main] - com.vmware.vim.installer.core.logging.CoreLoggerImpl.error(?:?) - Failed to established connection: com.microsoft.sqlserver.jdbc.SQLServerException: Login failed for user 'vCenterSSO_DBA'. Reason: The password of the account must be changed.
Please deselect the 3 password policy or change your SQL password more complexitily.