I do recall seeing reports of this. I'm not sure where I saw it in combination with an update, but see here
You can try one of the following:
- Connect your Touch to the computer and start Adobe Digital Editions (ADE).
- If ADE says the Touch is authorised, deauthorise
- Authorise the Touch again
2. Re-send books from ADE to the Touch (copy over existing, or delete existing first)
3. Uhmm... I'll have a think. Let me know if the above doesn't work.