Works fine in 3.5.6
Steps to reproduce:
Build the project for Windows x86 with "development built" checked. This is needed only to see the error message on the screen. This option does not affect behaviour of this bug in any way.

I attached two "Foo" files (js and cs). Please note that this is happening when Foo.cs is defined with at least one inspector variable.

This configuration worked fine with Unity 3.5.