pgAdmin crashes when client_min_messages is set in postgresql.conf

I am trying to get some query trees to appear in the PostgreSQL log and
in order to that I have set
client_min_messages = DEBUG1 in order to use the following settings
debug_print_parse, debug_print_rewritten, or debug_print_plan which are
required for the query tree to show up in the log.

pgAdmin crashes whenever I set that option. I tried a few times and I am
sure of it.
I am using PostgreSQL 7.4 under Cygwin on a Windows 2000 machine, but I
don't think that has any relevance.

I am sorry if this appears in some formatted font, I can't seem to set
the mail client to change to plain text.

PS. I wanted to set that option because I want to learn about the rule
system. Any pointers in that area?