With Attachments configured to a UNC path, you may receive the following error when trying to access previously added Attachments.

System Message 28175

SQL Error Encountered: Cannot set application role 'MSDSL' because it does not exist or the password is incorrect.

If you encounter the above, the cause may be that you have a record for the same application database in two different system databases -- specifically the domain table.  (for instance, a test copy of your live DB's).  To resolve this issue, remove or rename one of the references to the application DB from one of the two system databases.  Make a good backup before doing any updates or deletes.