As some people have found out, implementing the css adapters in MOSS 2007 can be quite frustrating. Even for myself.
After half a year of doing nothing with MOSS and wrapping up my old projects. I started working with MOSS again. Off course I wanted to work with te latest version of MOSS with the latest version of the CSS-Friendly adapters.
Both versions were upgraded and my previous described solution didn't work anymore. So I needed to get back to the drawing board.
Actually the basics of my solution still stands, but MOSS doesn't uses the ASP.BrowserCapsFactory from the Global Assembly Cache anymore. So you need to copy the CssAdapter.browser file to your MOSS websites App_Browsers directory (C:\Inetpub\wwwroot\wss\VirtualDirectories\80\App_Browsers). You actualy need to do this for each of your MOSS-website.
While I was at it I also needed to figure out a way to stop all the menu controls from using the CSS-Friendly controls in MOSS. That was actualy quite easy. In the WebControlAdapterExtender.cs is a boolean called "AdapterEnabled", you need to alter this property. This property automaticly assumes that every control will use the adapter. We want to invert this. So that the adapter is standard disabled. In your MOSS code you can add the attribute AdapterEnabled="true", if you want to enforce the adapter on your control. It will look something like this:
Thats is for now, if you encounter any problems don't hesitate to send me a note.