rails + paperclip + plupload

Question

Hi i'm using paperclip and plupload like in this tutorial: http://www.theroamingcoder.com/node/50

It works. But if i try to set thumbnails with paperclip like:

has_attached_file :data, 
    :styles => { :medium => "558x418>", :thumb => "60x82>" }

It doesn't work. I receive this error:

[paperclip] identify -format %wx%h '/tmp/stream20110209-26212-1l2obtp-0.png[0]' 2>/dev/null
[paperclip] convert '/tmp/stream20110209-26212-1l2obtp-0.png[0]' -resize "558x418>" '/tmp/stream20110209-26212-1l2obtp-020110209-26212-cl5lbg-0' 2>/dev/null
[paperclip] An error was received while processing: #<Paperclip::PaperclipError: There was an error processing the thumbnail for stream20110209-26212-1l2obtp-0>
[paperclip] identify -format %wx%h '/tmp/stream20110209-26212-1l2obtp-0.png[0]' 2>/dev/null
[paperclip] convert '/tmp/stream20110209-26212-1l2obtp-0.png[0]' -resize "60x82>" '/tmp/stream20110209-26212-1l2obtp-020110209-26212-1m6qvkj-0' 2>/dev/null
[paperclip] An error was received while processing: #<Paperclip::PaperclipError: There was an error processing the thumbnail for stream20110209-26212-1l2obtp-0

How can i solve it?

thanks