We have as SSL Porta running on a Cisco ASA 5505l that some of our external customers are using, and some of them are using IE 8/9
The thing is, the first time a new customer login on the portal and clicks one a RDP object they have to install the Cisco SSL VPN Forwarder, but are unable to to so because the Remote Desktop window ends up on top.
If you click connect you just end up back on the start page of the portal, and the install bar for the forwarder disappears.
If you click cancel, you just get a 404 error, (if you're fast, like 2 seconds, you might be able to install the forwarder)
This is a ASA 5505 running 9.1.1 and ASDM 220.127.116.11 and latest RDP plugin (09112012)
The same thing happened with a RDP plugin from 2009, ASA version 8.4.1 and ASDM 6.4.9
It works if you use java, or any other browser (also java of course), but we want this to be a seamless as possible, and many users are still stuck with IE unfortunately.