ERROR Errno::EINVAL: Invalid argument - <STDOUT> while uploading image with paperclip - ruby-on-rails

Question

I'm using Paperclip with ActiveAdmin to upload pictures in Articles.
But I have a problem, when I'm editing an existing article, the first time after Webrcik started, it functions very well. But systematically, the second time I try to edit an article (whatever the one) Windows tells me that "file.exe" stopped to function, and " Internal Server Error Invalid argument - STDOUT " appears in the browser.
So, I restart webrick, and upload works only one time etc...
Here's the log :
Started PUT "/admin/articles/1" for 127.0.0.1 at 2012-10-24 18:11:45 +0200
Processing by Admin::ArticlesController#update as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"VaB3lx3UZaOjUA6Yh+h8jG7ZExSQZDiyZUw6GYJQPbY=", "article"=>{"title"=>"ee", "desc"=>"ee", "content"=>"eeee", "photo"=>#<ActionDispatch::Http::UploadedFile:0x3cce7f0 #original_filename="Desert.jpg", #content_type="image/jpeg", #headers="Content-Disposition: form-data; name=\"article[photo]\"; filename=\"Desert.jpg\"\r\nContent-Type: image/jpeg\r\n", #tempfile=#<File:C:/Users/Greg/AppData/Local/Temp/RackMultipart20121024-6620-oorxwu>>}, "commit"=>"Update Article", "id"=>"1"}
[1m[35mAdminUser Load (0.0ms)[0m SELECT `admin_users`.* FROM `admin_users` WHERE `admin_users`.`id` = 2 LIMIT 1
[1m[36mArticle Load (1.0ms)[0m [1mSELECT `articles`.* FROM `articles` WHERE `articles`.`id` = ? LIMIT 1[0m [["id", "1"]]
Command :: identify -format %wx%h "C:/Users/Greg/AppData/Local/Temp/Desert20121024-6620-16n1ehl.jpg[0]"
Command :: identify -format %m "C:/Users/Greg/AppData/Local/Temp/Desert20121024-6620-16n1ehl.jpg[0]"
Command :: identify -format %m "C:/Users/Greg/AppData/Local/Temp/Desert20121024-6620-16n1ehl.jpg[0]"
Command :: convert "C:/Users/Greg/AppData/Local/Temp/Desert20121024-6620-16n1ehl.jpg[0]" -auto-orient -resize "510x" -crop "510x350+0+16" +repage "C:/Users/Greg/AppData/Local/Temp/Desert20121024-6620-16n1ehl20121024-6620-mvfl3a"
Command :: file -b --mime "C:/Users/Greg/AppData/Local/Temp/Desert20121024-6620-16n1ehl20121024-6620-mvfl3a"
[paperclip] Error while determining content type: Command 'file -b --mime :file' returned 255. Expected 0
Command :: identify -format %wx%h "C:/Users/Greg/AppData/Local/Temp/Desert20121024-6620-16n1ehl.jpg[0]"
Command :: identify -format %m "C:/Users/Greg/AppData/Local/Temp/Desert20121024-6620-16n1ehl.jpg[0]"
Completed 500 Internal Server Error in 22073ms
Errno::EINVAL (Invalid argument - ruby_setenv):
I've been searching for a solution...but I did not find one.
Does someone have an idea of the source of the problem ?

Answer 1

The 'file' program isn't a part of Windows, which suggests you installed it (or something that includes it) to get this far - any idea what that was? Gnu provides a Windows version of 'file' as part of GnuWin32.
Learning more about your copy of that program will probably be the first step to fixing your problem. (Hope this helps.)