The issue was something like there are some references into the application from the network shared folder. When compiling the application there was a weird error saying (or similar):

The “ValidateXaml” task failed unexpectedly.
System.IO.FileLoadException: Could not load file or assembly ‘file://\\xxxxxxxx\Assemblies\xxxxx.dll’ or one of its dependencies. Operation is not supported. (Exception from HRESULT: 0x80131515)
File name: ‘file://\\xxxxxxxx\Assemblies\xxxxx.dll’ —> System.NotSupportedException: An attempt was made to load an assembly from a network location which would have caused the assembly to be sandboxed in previous versions of the .NET Framework. This release of the .NET Framework does not enable CAS policy by default, so this load may be dangerous. If this load is not intended to sandbox the assembly, please enable the loadFromRemoteSources switch. See for more information.

The solution is quite simple.

Edit you app.config file (if you don’t have it, just add it to your project):

<?xml version="1.0"?>
  <startup useLegacyV2RuntimeActivationPolicy="true">
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5"/>
    <loadFromRemoteSources enabled="true"/>

The key is the loadFromRemoteSources tag, fixing this annoying error.

Look here for more details.