Bug in Postgres 6.4?

I'm running 6.4 on a LinuxPPC box. I have an 8MB table of mailing list
archives, mostly big TEXT fields.

I was trying to create a index on the text field AFTER the table was
populated (shouldn't cause problems, right?). And I got these errors:

>CREATE INDEX idx_mail_body ON tbl_mail_archive (fld_mail_body);

java.sql.SQLException: FATAL 1:  btree: failed to add item to the page in
_bt_sort (2)

 java.lang.Throwable(java.lang.String)
 java.lang.Exception(java.lang.String)
 java.sql.SQLException(java.lang.String)
 postgresql.ResultSet postgresql.Connection.ExecSQL(java.lang.String)
 boolean postgresql.Statement.execute(java.lang.String)
 int postgresql.Statement.executeUpdate(java.lang.String)
 void
com.geocrawler.common.util.SQLInterface.buttonPerformSQL_ActionEvents()
 void com.geocrawler.common.util.SQLInterface.connEtoC1()
 void
com.geocrawler.common.util.SQLInterface.actionPerformed(java.awt.event.Actio
nEvent)
 void java.awt.Button.processActionEvent(java.awt.event.ActionEvent)
 void java.awt.Button.processEvent(java.awt.AWTEvent)
 void java.awt.Component.dispatchEventImpl(java.awt.AWTEvent)
 void java.awt.Component.dispatchEvent(java.awt.AWTEvent)
 void java.awt.EventDispatchThread.run()

Using PSQL I tried to drop the index:

db_domain-> DROP INDEX idx_mail_body;
ERROR:  parser: parse error at or near "drop"
db_domain=> CREATE INDEX idx_mail_body ON tbl_mail_archive (fld_mail_body);
ERROR:  cannot create idx_mail_body
db_domain=> DROP INDEX idx_mail_body;
ERROR:  index "idx_mail_body" nonexistent