If you had put sensitive data, always make sure you have to copies, one on the NAS and the other somewhere else.
I had power issues in the past but my 320 did recover every time, even got the email alert!
one question, you mentioned you pushed the power button for 3 seconds. Did you push it until it went off? Or did you push it and release, after a couple of seconds LEDs blink and it goes off?
Wondering if you did a hard reset or an actual shutdown.