Attachement_fu max_size problem...mystery...need help please

Hi All,

Just to share with you, after many hours of hair scratching, 10 cubs
of coffee and sleepless night, i finally got attachement_fu creating
thumbnail for me...

BUT, there is a mysterious problem i encounter.

What i learnt
1. I realize that i must create a parent_id in the photos table
according to the instruction, othewise, thumbnail wont get generated.

What I dont understand
1. I dont know why i cant allow a bigger file size to be uploaded.
Consider below photo.rb model file i got

has_attachment :content_type => :image,
               :storage => :file_system,
               :processor => 'Rmagick',
               :path_prefix => 'public/files',
               :thumbnails => { :thumb => [50, 50]},
               :max_size => 3000.kilobytes

validates_as_attachment

Now, the max_size => is 3000 kilobytes, meaning 3kb ? even i changed
it to 30000.kilobytes, it does not allow me to upload file size
smaller than that.

I got this error..

1 error prohibited this photo from being saved

There were problems with the following fields:

    * Size is not included in the list

The error message is rather misleading, I GUESS its trying to say
"File Size exists limit"..but i have no idea.

Any suggestion will be good ?