Ack! This happened to me today.
I was halway through reading a DRM book & it just started to restart over & over. I had to re-set it to get it to stop.
After a couple of hours I tried plugging it into my PC & let the Sony reader software re-activate it - didn't work.
I tried updating ADE to v1.8 preview hoping that might do the trick.
In the end the only thing that worked was using the reader itself - I went online through the Sony Store, logged in & it automatically authorised itself.
It's always the last thing you try isn't it
