Cannot change target framework of a PCL

Question

I'm trying to create a cross platform project in order to reuse most of the code in a Windows Phone (7.5) and a WinRT simple game. I'm trying to use a Portable Class Library, now that there's an official support for async operations inside WinPhone 7.5 projects (Microsoft.Bcl.Async). I'm having issues installing the NuGet Package for the Bcl.Async (cannot find a compatible framework), and after googling around i've discovered that the problem is that i was targeting Windows Phone 7 (not the required 7.5) for my PCL project.

The problem is that if i try to target WinPhone 7.5 i receive this message:

Why i cannot target Windows Phone 7.5? Is there a way to force that? (Sorry, maybe this is a truly noob question...but i can't find an answer anywhere). Please also note that this is a valid combination of framework, as stated in the msdn guide that you can find here: http://msdn.microsoft.com/en-us/library/gg597391.aspx.

Answer 1

I've found a solution for this problem...and i was the cause =) I'm trying to use MvvmCross and Xamarin in order to write a cross-platform code, but i've made some mistakes when i've changed the Profile104 to provide the Mono for Android target for my PCL. Removing this resolved my issue.

Thanks to everyone for your answers anyway.