statistics collector process is thrashing my cpu

Dear All

Sometimes postgres.exe will thrash one of the cores and won't stop
until I kill the process. I know it's the statistics collector as I
get this message when I kill the process:
"statistics collector process (PID 172) exited with exit code 1"
Nothing other than this app is accessing my PG server.

I'm developing a web mapping application which retrieves point data
via multiple statements like this:

 select xmlelement(name "amr:mapFeatureType",
xmlattributes(featuretype as name),xmlagg(
                xmlelement(name "amr:mapFeature", xmlforest(y(the_geom) as
"amr:latitude", x(the_geom) as "amr:longitude", lable as
"amr:description"))
                ))
            from (select featuretype, the_geom, lable from poi
                    WHERE the_geom && setsrid(
                            'BOX3D(-5.625 52.482780222078205,0
55.7765730186677)'::box3d, 4326)
                    and featureclass = 'layer3'
                    limit 15) as ss
             group by ss.featuretype

I don't even know why this process would run anyway, as I haven't
updated the database for weeks (it's only a dummy dataset).

I'm also getting hundreds of these messages in a few hours work:
2008-05-08 09:22:56 BST LOG:  loaded library
"$libdir/plugins/plugin_debugger.dll"
2008-05-08 09:22:56 BST LOG:  loaded library
"$libdir/plugins/plugin_debugger.dll"
Why would it load it twice within the same second?

Select version() - "PostgreSQL 8.3.1, compiled by Visual C++ build 1400"
Machine - XP sp2, core 2 duo 7250 laptop

The only non 'out of the box' setting I've changed in postgresql.conf is:
log_statement = 'all'

Any ideas why this might be happening, and how I can stop it?

Thanks,

Will T