HTTP Status 404 after installing plugins from Marketplace

I had Pentaho up and running and went into Marketplace to install C-Tools(CDE, CDF & CDA) & Saiku Analytics as detailed here; http://pentaho-bi-suite.blogspot.co....erver-501.html

Now after restarting the server I'm getting a 404. I can't even get to the login page. Can a Pentaho server really be completely trashed by the install of a plug-in?