Why do I get an error code from growl when using grunt-notify?

Question

I installed grunt-notify to get messages on desktop.

Here is the Gruntfile.js :

module.exports = function(grunt) {
  grunt.initConfig({
    notify: {
      test: {
        options: {
          message: "YO"
        }
      }
    }
  });

  grunt.loadNpmTasks('grunt-notify');

  // simplified example
  grunt.registerTask('default', ['notify:test']);
};

The console output on grunt -v

E:\Temp>grunt -v
Initializing
Command-line options: --verbose

Reading "Gruntfile.js" Gruntfile...OK

Registering Gruntfile tasks.
Initializing config...OK

Registering "grunt-notify" local Npm module tasks.
Reading E:\Temp\node_modules\grunt-notify\package.json...OK
Parsing E:\Temp\node_modules\grunt-notify\package.json...OK
Loading "notify.js" tasks...OK
+ notify
Loading "notify_hooks.js" tasks...OK
+ notify_hooks
Loading "Gruntfile.js" tasks...OK
+ default

No tasks specified, running default tasks.
Running tasks: default

Running "default" task

Running "notify:test" (notify) task
Verifying property notify.test exists in config...OK
File: [no files]
Options: title="Temp", message="YO"
>> [grunt-notify] growl: C:\Utils\growlnotify\growlnotify.COM
>> [growl] cmd: growlnotify
>> [growl] args: /i:E:\Temp\node_modules\grunt-notify\images\grunt-logo.png  YO /t:Temp
>> [growl] return_code: 4294967295

Done, without errors.

We can see a return_code: 4294967295 (-1 converted to unsigned 32-bit value). .

If I manually do the following command line : E:\Temp>growlnotify /i:E:\Temp\node_modules\grunt-notify\images\grunt-logo.png YO /t:Temp

I got the message (without the logo) :

So, why I got an error code when passing via grunt-notify, but not on a manual line command?

Note : I'm using Windows 7 Pro

Edit : after following this issue : https://github.com/dylang/grunt-notify/issues/91, I succeed to get the image with the command line :

C:\temp>growlnotify /i:"C:/temp/node_modules/grunt-notify/images/grunt-logo.png"  "YO" /t:temp

But still doesn't work through grunt...