Java error and CSS still the same
I renamed the Configuration file Configuration_back and uninstalled the Site Assist extension. After re-installing a fresh copy from the website all is exactly the same.
The 'gettreenode' java error appeared again - but I guess it is because I tried adding a Links page to the navigation. I think there is a clash because Site Assist automatically allows for a Links page in the footer section and presumably it doesn't like 2 pages with the same name. I had the same problem trying to create a page called Contact. When I then called it Contact Us - it was OK. I use the mouse to select the type to rename it and then hit return to OK it.
Hopefully that may be the reason for the Java error which I can sort of understand.
However the CSS is still all wrong. The fonts requested aren't used, the images don't appear and I still get 'undefined' after all the links in the footer.