ERROR: index "patient_pkey" is not a btree

hi
i am having postgres version 8.0.0 installed, on my machine

i created a database and the tables and the stored procedures for the same

however i get this error, while trying to execute an insert command, in postgreslog

PL/pgSQL function "insert_patient" line 20 at SQL statement
<2006-09-21 03:35:45 IST%SELECT>ERROR: index "patient_pkey" is not a btree
<2006-09-21 03:35:45 IST%SELECT>CONTEXT: SQL statement "insert into patient(patient_name,org_pat_id,birth_date,patient_key)
values( $1 ,trim( $2 ), $3 ,trim( $4 ))"

please tell what may be going wrong,
this is what i did, i just recreated the database and the tables and then everything worked fine.

thanks,
regards
Surabhi