What OS are you using? It sounds like you were tossed into Open Firmware
Try this;

1. type: reset-nvram
2. Press Return.
3. If prompted for your password, enter it and press the Return key. It will respond OK.
4. At the Open Firmware prompt, type: set-defaults
5. Press Return. It will respond OK.
6. At the Open Firmware prompt, type: reset-all
7. Press Return.

Hope this helps,
Dave