Just getting started with the new 3.0 release. I've installed the source code and reference library and changed build path as directed in the help files. There are no errors showing up in Flash Builder but when I run the application I just get a blank web-page (esri logo loads in bottom right after about 5 seconds - title on tab shows as ArcGIS Viewer for Flex). I've previously worked exactly the same way with Flex Viewer 2.5 and had no issue. I'm installing the source code to a local installation on Windows 7.
If I open the the index.html directly from C:\inetpub\wwwroot\FlexViewer30_debug rather than as http://localhost/FlexViewer30_debug then I get an error message popup as
Fault code: InvokeFailed
Fault info: Error #2148
Fault details: null
I'm assuming it's some kind of IIS configuration issue but I have no issue running 3.0 apps created using the application builder.