How to make hal pick reliably up a new configuration file

[Michael T]

Dear List,

I assume that I am overlooking something obvious to you here, but I really have
no idea what it is, so I would be very grateful for any hints.  I have the
following problem with hal on at least vanilla-from-installer-CD Ubuntu 8.10
systems and the Ubuntu 8.10 live CD.  I would like to have an X.Org mouse driver
(specifically the VirtualBox guest mouse driver) advertised by hal.  To achieve
this, I copy the following file:

90-vboxguest.fdi:
<?xml version="1.0" encoding="UTF-8"?>
<!--
[snip]
-->
<deviceinfo version="0.2">
  <device>
    <match key="info.subsystem" string="pci">
      <match key="info.product" string="VirtualBox Guest Service">
        <append key="info.capabilities" type="strlist">input</append>
        <append key="info.capabilities" type="strlist">input.mouse</append>
        <merge key="input.x11_driver" type="string">vboxmouse</merge>
        <merge key="input.device" type="string">/dev/vboxadd</merge>
      </match>
    </match>
  </device>
</deviceinfo>

into /usr/share/hal/fdi/policy/20thirdparty and restart hal (/etc/init.d/hal
restart).  Sometimes this succeeds and lshal | grep x11 shows the right entry. 
Sometimes, in apparently identical setups, this fails.  Usually after rebooting
and/or updating the system a few times it starts to work (obviously this does
not apply when using the live CD).

Can someone point me at what I am doing wrong here?

Thanks very much!

Michael