When v3 of the Scrum for Team System process template was released, it was incompatible with Sharepoint 2010, and the portal would not install. Crispin Parker has since released a .wsp that can be used with Sharepoint 2010, but it is a simple recompile of the 2007 site and has many errors, as blogged about by Richard Fennel.
Luckily, VS2010 includes a Sharepoint project type that is able to decompile a .wsp for editing.
Following the initial steps already documented on Richard’s blog I was able to get a working portal up and running fairly quickly. The result is a Sharepoint 2010 version of the portal that fixes all of the issues while following the style of the other TFS process templates: