Image style doesn't rebuild after image style flushed

Question

I have practically the same problem as here : https://drupal.org/node/2187443

I've flushed my image style because I edited this image style. Now when I reload the page where the image style should be shown they are missing (404).

What did I missed? shouldn't it be recreated automatically when styles are removed ?

Edit :

I found that images couldn't regenerate if 404 error isn't managed by Drupal. I think its very possible, then I made a change in to my .htaccess file to make Drupal manage 404 errors.

I am now getting the 403 error upon all my files, that are still not loading. :(

Failed to load resource: the server responded with a status of 403 (Forbidden) 

Then I add +w on my files directory recursively to make sure the writing permission available for all to avoid 403 but nothing happens.

Answer 1

Problem solved!!!

After checking that Drupal manages itself 404 errors by checking .htaccess file :

# Make Drupal handle any 404 errors.
ErrorDocument 404 /index.php

I had to put this line into my settings.php... This is in the Drupal 7.20 release notes :

$conf['image_allow_insecure_derivatives'] = TRUE;

This thread saved my day.

Wish helps others.