You'll get this message if the [operating systems] section is missing. It will boot normally to whatever you have specified in default= under the [boot loader] section.
If you boot.ini is completely missing, junk or unreadable it will boot normally only if you're booting to multi(0)disk(0)rdisk(0)partition(1).
When in doubt, boot to recovery console and use the "map arc" command to see how to rebuild your boot.ini.