Windows Store (WP 8.1) errors while building

Hi,

I'm porting a Unity game from Android/iOS to WP8 but when I try to build (from build settings), it throws a lot of errors like these:

 error CS0103: The name 'Console' does not exist in the current context error CS0234: The type or namespace name 'FileStream' does not exist in the namespace 'System.IO' (are you missing an assembly reference?) error CS0246: The type or namespace name 'Thread' could not be found (are you missing a using directive or an assembly reference?) ...

I have the correct "using" directives and I don't have any problem with Android/iOS builds nor in Unity Editor.

My build settings are:

• Platform: Windows Store

• Type: XAML C# Solution

• SDK: Phone 8.1

Any ideas?

Thanks.