Audigy Platinum Won't Record From Mic & MIDI

It's worked fine for a year. I record vocals and acoustic guitar in Sonar 2
on Win XP Pro.

Suddenly I can't record anything from the microphone. I restored my OS from
an image to a time when the Audigy worked fine, but it made no difference so
I don't think it's a software problem.

The record meters in Sonar and the Creative recorder show no input activity
at all. The microphone's okay - my kid can record in his karaoke program no
problem.

I can't record MIDI soft synths using the piano keys on the Sonar piano roll
either - nothing appears in the track view. But I can record a visible,
replayable MIDI track by step-entering notes with the mouse.

The mixer's set to record from Line-in 2/Mic 2 and no settings have been
changed from when it all worked fine.

Anyone seen anything like this before? Thanks for your help,

Mike