I had a kernel 3 error this morning. I found this old post via search result.
My fix was in the Site Setting of the override/siteaccess/[your-site-access]/site.ini.append.php file. The previous site used this to route the default & index pages to a root folder (node 64).
On my new site, I swapped the Homepage (node 2) with the root folder (node 64). So now the root is the Homepage. Then I deleted the folder.
The Default path is "content/view/full/2" so I didn't need these lines. I commented them out and everything is working again!