Pltcl error - could not create "normal" interpreter

Greetings,

Could somebody shed any light on the error message below that came from
trying to call a simple pltcl test function? I am running Postgres 8.1
on WinXP and just recently added the pltcl language by copying Tcl84.dll
into my system directory (C:/Windows/System32) and successfully issuing
the command:
> createlang pltcl -U db_admin postgres
What else do I need to do or configure to enable this full
functionality?

postgres=# create or replace function test_fxn() returns void as $$
postgres$# spi_exec "SELECT * FROM test"
postgres$# $$ language pltcl;
CREATE FUNCTION
postgres=# select test_fxn();
ERROR: could not create "normal" interpreter
postgres=#

Any help is greatly appreciated and the little that's in the
archives/www is fairly abstruse. Thanks,
JL