Solved! Go to Solution.
Since there is no forum for Server 10.2 yet, I'll post this here:
I've installed the Web Adaptor 10.2 for IIS on my web server and now I want to install it again for a second access point, as the installation instructions say I can (http://resources.arcgis.com/en/help/install-guides/arcgis-server-web-adaptor-iis/10.2/index.html#/In...). However, when I try to install it a second time, it just brings up the dialog asking me whether I want to modify, repair or uninstall the software. It won't let me install it a second time. Web server is running on Windows 2012 R2 Preview. A bug or is this just Windows causing problems?