[horde] IMP won't display full message headers

[Adam Lewicki]

Happy new year folks,
I'm having an issue here with IMP that I cannot quite wrap my head around...

In the configuration web-view I have enabled the option for users to  
view the full message headers.
The conf.php file gets written on the server and the setting is there.

---
<?php
/* CONFIG START. DO NOT CHANGE ANYTHING IN OR AFTER THIS LINE. */
// $Id: xxx $
$conf['user']['allow_view_source'] = true;
$conf['server']['server_list'] = 'none';
...etcetc
---

during troubleshooting i also created a conf.local.php with a single line:
$conf['user']['allow_view_source'] = true;
in it, to make sure no other 'previous' configuration directives  
prevent something.

But I can't seem to get the "view message headers" option neither in  
preview nor in the full message view in horde.
It simply doesn't show up.

When I log out and re-login with 'basic' view (instead of dynamic) I  
see the option and it works fine, it seems to be a problem with  
dynamic view.
All my Horde Components are up to date, I just did a pear update yesterday.

So can anyone of you guys send me into the right direction with my problem?

Best wishes

Adam