If you are responsible for your Roundcube installation then check the Roundcube error log (default location: [rc root]/logs/errors) also have a look at the responses table in your database, if the responses are still there then may be you have 2 user profiles, that can happen if the mail_host changes, have a look in the users table for that.
If you don't have access to any of that then you need to talk to whoever is responsible for your webmail/your email provider.
