Can you get you enable imap_debug option in Roundcube and check logs/imap file.
I haven't done that but I'm using hMailServer as my email server on Windows Server 2003 and I just started a log in hMailServer and tried to log in. I entered my correct login info for
myname@mydomain.com into roundcube webmail. Here's what I saw in hMailServer logs. Looks like it logs out right away, not sure if this is normal. Nothing else in the logs after 5 minutes or so and roundcube is still at the login page showing "Waiting..." down in the taskbar of the browser.
"TCPIP" 3892 "2010-01-10 01:27:03.448" "TCPConnection - Posting AcceptEx on 0:0"
"DEBUG" 3892 "2010-01-10 01:27:03.464" "Creating session 34"
"IMAPD" 3892 34 "2010-01-10 01:27:03.464" "127.0.0.1" "SENT: * OK ::Welcome::"
"IMAPD" 3892 34 "2010-01-10 01:27:03.464" "127.0.0.1" "RECEIVED: cp01 CAPABILITY"
"IMAPD" 3892 34 "2010-01-10 01:27:03.464" "127.0.0.1" "SENT: * CAPABILITY IMAP4 IMAP4rev1 CHILDREN IDLE QUOTA SORT ACL NAMESPACE RIGHTS=texk[nl]cp01 OK CAPABILITY completed"
"IMAPD" 3892 34 "2010-01-10 01:27:03.464" "127.0.0.1" "RECEIVED: a001 LOGIN "myname@mydomain.com" ***"
"IMAPD" 3892 34 "2010-01-10 01:27:03.495" "127.0.0.1" "SENT: a001 OK LOGIN completed"
"IMAPD" 3892 34 "2010-01-10 01:27:03.573" "127.0.0.1" "RECEIVED: I LOGOUT"
"IMAPD" 3892 34 "2010-01-10 01:27:03.573" "127.0.0.1" "SENT: * BYE Have a nice day[nl]I OK Logout completed"
"DEBUG" 3940 "2010-01-10 01:27:03.589" "Closing TCP/IP socket"
"DEBUG" 3940 "2010-01-10 01:27:03.589" "Ending session 34"