Thanks, Alec.  It still fails if I set a delay on marking the message as read.  If I change the setting to immediately, Roundcube works as expected.

On 2014-12-25 3:06, A.L.E.C wrote:

On 12/24/2014 05:48 PM, Steve Fintel wrote:

I upgraded an RC 0.9 installation to RC 1.0.4. I have clients set to automatically mark messages as read after 5 seconds. When I view an unread message for more than 5 seconds, I get the following error message: Server Error: SELECT: Client tried to access nonexistent namespace. (Mailbox name should probably be prefixed with: INBOX.)

Try this patch:
https://github.com/roundcube/roundcubemail/commit/acbf70d5bdbfa179

If it does not help, enable imap_debug and provide the log.