Suddenly it thinks there's no toner.  Page count is 5276.

http://www.fixyourownprinter.com/forums/laser/39806

Tried this

1. Switch off
2. Hold down Go button while switching on
3. Release Go, then press 2 times, pause for lights to all stay on, press 5 times.

Does some sort of reset — had to re-do static IP address again afterwards.