pg_log >> groving to infinity in 6.5.1

Hello in 6.5.1 i noticed this strange behavior;
I have databaze vith about 50 table and the whole amount of date in them
is aprox 30M.
But the size of pg_log after a two weeks of osing the db is 0.5G !!?
I am using large object - so the dump and reload is rathe painfull. I have
script which dumps the db ewery week removes all files and initlocation,
ititbd createusers ....
But that's rather strange solution.
I am using the db for fulltext search soi there are some big tables of
words and big referencig tablese between words and records in other
tables.
This table are deleted and rebuild ewery night.
Is there any way how to tell to postres to shring the pg_log?

Thank You very much.

Richard Bouska
Richard(at)Bouska(dot)cz

PS: I tryed to find some hints on dejanews and in archives, but fond
nothin promising the solution.; vacuum verbose analyze does not help.