I want to protect both WMS served video, and IIS served webpages with Basic Authentication, but I
only want the user prompted once.
Since IIS and WMS use a different protocol, and different browser/server player/server combinations, the first time they access web pages they will be prompted for password, and the first time they access video, they will be prompted.
You could try VideoQuota protecting by referrer, and only allow referrers from your own website, and see if that works for you. That won't prompt for videos, but still restrict their access.
The latest version of VideoQuota (5/5/08) does allow for single sign-on! Contact us for details...