Click on 'Submit a web case'
** You may need to log in with your AdobeID
Under 'Get Support', in the 'Techinical Support' tab
For "Choose issue type" select "Using a product or service"
For "Choose product", first select "Additional Products"
Then select "Adobe Digital Editions"
Then select "Continue"
In the next screen provide as much information as you can, preferably including the exact and full text of the error message.