This problem occurs with the Cisco VPN 3000 Series Concentrator, Release 4.1.7 or 4.7, and is due to the presence of Cisco bug ID CSCsb06794.
When the Cisco IOS WebVPN URL redirection or web mangling feature is used to connect to the Domino server, Domino Web Access 6.5.4 is accessible. However, no further function can be performed. During an attempt to open mail, an error message appears. When the error message box is closed, the mail contents are not displayed.
As a workaround, use an IPSec VPN client or a Secure Socket Layer (SSL) VPN client.