This problem is related to IE9 security.
Blue Coat has verified that if you select SSLv3 only for ‘Security’ under IE9 Internet Options/Advanced, you will not get this error message. However, if you select TLSv1.0 (uncheck TLSv1.1/1.2), you will see the "400 bad request" message.
This could be a minor issue in TLSv1.0 implementation.
If the above does not fix the issue and you are accessing PacketShaper via HTTPS, another workaround is to uninstall the patch below:
Security update for Microsoft Windows (KB2585542)
Please ensure PacketShaper is running v8.7.4 and above. The PacketWise code has been modified to accommodate the Microsoft patch, allowing users to access PacketShaper using HTTPS on IE 9 and FireFox 10.