[TYPO3-english] imagemagick path saving to localconf but not working

[Simon Browning]

typo3 4.2.1
php 5.2.6

In the install tool I've specified the imagemagick path an it is being 
written to the localconf as:

$TYPO3_CONF_VARS['GFX']['im_path'] = '/cp/bin';

When the all config page reloads though, the imagemagick path section is 
empty and imagemagick functions aren't working through the site (image 
resizing, thumbnails in the backend, etc.)

On the Basic Config page, if I specify the IM path and send it does 
detect the IM install.

Am I missing something?

Thank you.

Simon