Known problem with Xamarin Studio 4.0.11 when loading 4.0.10 solution?

With a simple solution I started with Studio version 4.0.10 (it's only one line more than a default new project) and then opening with Studio version 4.0.11, I get this error msg:

Error while trying to load the project C:\Users\blah\blah\test.csproj: Value cannot be null Parameter name: source

Here's the .csproj file contents:

<?xml version="1.0" encoding="utf-8"?> Debug AnyCPU 10.0.0 2.0 {DCC2992E-2016-4654-8B0A-C609406435D4} {EFBA0AD7-5A72-4C68-AF49-83D382785DCF};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC} Library BT4_test True Resources\Resource.designer.cs Resource Resources Assets BT4_test v4.2 Properties\AndroidManifest.xml True true full false bin\Debug DEBUG; prompt 4 false None full true bin\Release prompt 4 false false