"sniffing" postgres queries

Hi,
I am having real trouble with a project that is a little out of my
league and I just can't find out how to find which table the app is
getting its values from (it's a long story...). I know what values I
am looking for, and would like to log everything (even if only for one
call of a web page...) that comes in and everything that goes out. Is
this possible at the db level? Even debug5 doesn't seem to give me the
result of a query... If it is only possible at the driver level (I did
something vaguely similar with the odbc driver I think), then any
pointers for a jdbc2 on 8.1.4?
Thanks
Anton