Querying SharePoint 2010 SPSite from within console application results in FileNotFoundException

Tried to connect to a SharePoint 2010 sitecollection via a console application today, but it kept failing with an FileNotFoundException.
Code:

using(SPSite site = new SPSite("http://sps2010"){
 //FileNotFoundException
}

Just for future reference:

1. make sure your application is using the .NET 3.5 framework
2. ensure it's compiled as 64 bit

As you'll have guessed by now: my app was using the visual studio 2010 default settings of .NET framework 4.0, compiled as x86 ... which obviously conflicts with the Microsoft.SharePoint assemblies (that are built on 3.5 and as 64bit.) :)