Please describe the problem:
It is not possible to change the trust of the key i signed.
The gui always displays : Trust: Marginal and the dropdown box is disabled. (as you can see in the screenshot)
@http://launchpadlibrarian.net/25888067/Screenshot-seahorse.png

the gpg command displayes 2 trust levels:
1. trust:marginal
2. [ full ]

$ gpg --edit-key <email address hidden>
gpg (GnuPG) 1.4.9; Copyright (C) 2008 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

pub 1024D/2A47CC28 created: 2009-04-05 expires: 2010-04-05 usage: SC
                     trust: marginal validity: full
sub 4096g/0871105F created: 2009-04-05 expires: 2010-04-05 usage: E
[ full ] (1). xx xx <email address hidden>

Steps to reproduce:
1. start seahorse
2. open Trusted Keys Tab
3. Properties on a key you have signed
4. details tab
5. > indicate Trust dropdown is disabled.


Actual results:
cannot change trust level

Expected results:
the user should be able to set the trust level. Like the gpg command is able to

Does this happen every time?
yes

Other information:
https://bugs.launchpad.net/ubuntu/+source/seahorse/+bug/365540