Upgraded to Alfresco 4.2.d and lost your application menu bar ...

It might be because of an share-config override like:

  <config evaluator="string-compare" condition="WebFramework" replace="true">

Try removing replace="true" and if you need to replace, your should look up surf.xml to add all the new definitions.

Preview, index, thumbnail SVG in Alfresco

In modern browsers SVG is directly supported, so previewing is a smaller task. Ne add-on for Alfresco with enhanced SVG support for previewing, thumbnailing and indexing (search)

See more:
https://addons.alfresco.com/addons/enhanced-svg-support
http://code.google.com/p/alfresco-svg/