We have it here too.
The "Clean Security Agent," if I'm not wrong, is the Cisco Clean Access Agent that comes with the Cisco NAC Appilance, which runs on Windows only, and is a pain esp. for those who are running Vista. This beast have to run under Administrator privilesges and pops up a login window everytime you connect back to the network, and doesn't even want to accept certain types of Anti-virus software (such as Avira.)
Workaround: It doesn't run on Mac and Linux. If you use WIndows, you can convince the NAC you're using Linux and it will believe it until the appliance gets restarted. If you have Linux - great, the NAC just let you pass through. If you have Windows, Kevin, a program with a great icon, used to work but recently it didn't, but there is always an easy way to get over it: boot into Linux and fire up firefox and click on a link, and then boot back to Windows.
And just FYI: Due to an insane number of complaints received from the students, the IT Staff over here is getting rid of the Cisco CCA this summer :-)