Hi qole, I read this thread and you seem competent to solve my problem.
On my N900 (running Maemo5) I installed dbus-switchboard. I ran dbus-switchboard-gui (with root user), and add a new Handler, and I add :
Abiword,cli,abiword %params%
to /usr/lib/dbus-switchboard/dbus-switch-apps.cfg.
I modified /usr/lib/dbus-switchboard/dbus-switch-xref.cfg :
.doc,Abiword,

I rebooted the device, but when I try to open a .doc file, I have a yellow banner saying "No handler configured for this type".
I tried to debug using :
dbus-switchboard.py
I get the following :
dbus-switchboard started
--
-- dbus-switchboard: Received an RPC to mime_open.
-- dbus-switchboard: RPC had arguments ['file:///home/user/MyDocs/.documents/MARTINS%20(IB).doc'].
--
-- params : file://%5B%27/home/user/MyDocs/.documents/MARTINS%20%28IB%29.doc%27%5D
-- params2 : %5B%27/home/user/MyDocs/.documents/MARTINS%20%28IB%29.doc%27%5D
-- realparams : file://['/home/user/MyDocs/.documents/MARTINS (IB).doc']
-- realparams2 : ['/home/user/MyDocs/.documents/MARTINS (IB).doc']
--
no handler found

So I don't understand why dbus-switchboard doesn't found my handler, and finally open the file using Abiword.
Could you help me a little ?