[Tracker] No contents indexing taking place

[Karl Relton <karllinuxtest relton ntlworld com>]

Tracker 0.12 in Ubuntu Precise Pangolin doesn't seem to be indexing any
file contents at all these days - not even words in plain text files.

But I see in tracker-miner-fs.log :

29 Feb 2012, 21:18:57: Tracker: tracker-backend.vala:84:
Tracker.Sparql.Backend.query_async(): 'SELECT ?s WHERE { ?s nie:url
"file:///home/parents/Documents/how_about3.txt"}'
29 Feb 2012, 21:18:58: Tracker: Processing file
'file:///home/parents/Documents/how_about3.txt'...
29 Feb 2012, 21:18:58: Tracker: Processed 0/0, estimated unknown time
left, less than one second elapsed
29 Feb 2012, 21:18:58: Tracker: Loading extractor rules...
(/usr/share/tracker/extract-rules)
29 Feb 2012, 21:18:58: Tracker:   Loaded rule '10-abw.rule'
 <... snip ...>
29 Feb 2012, 21:18:58: Tracker:   Loaded rule '90-text-generic.rule'
29 Feb 2012, 21:18:58: Tracker: Extractor rules loaded
29 Feb 2012, 21:19:00: Tracker: Could not process
'file:///home/parents/Documents/how_about3.txt':
GDBus.Error:org.freedesktop.DBus.Error.UnknownMethod: No such interface
`org.freedesktop.Tracker1.Extract' on object at
path /org/freedesktop/Tracker1/Extract
29 Feb 2012, 21:19:00: Tracker: Flushing SPARQL buffer, reason: Queue
handlers NONE
29 Feb 2012, 21:19:00: Tracker: (Sparql buffer) Finished array-update
with 1 tasks
29 Feb 2012, 21:19:00: Tracker: Idle
29 Feb 2012, 21:19:00: Tracker: Finished mining in seconds:2.301661,
total directories:0, total files:0


I guess that UknownMethod message is bad news, stopping the extractor
from actually being called.

What would cause this - is there some dbus configuration file missing? I
see the interface is defined in /usr/share/tracker/tracker-extract.xml
(the same as in oneiric, as far as I can tell).

Regards
Karl