DROP INDEX causes errors

# select version();
version
-------------------------------------------------------------------------------------------------------------------
PostgreSQL 8.1.11 on x86_64-unknown-linux-gnu, compiled by GCC gcc
(GCC) 4.1.2 20061115 (prerelease) (SUSE Linux)

Today I dropped an index:
DROP INDEX dbmail_messageblks_physmessage_idx ;

The table is now:
# \d dbmail_messageblks
Tabelle »public.dbmail_messageblks«
Spalte | Typ | Attribute
-----------------+----------+------------------------------------------------------------------
messageblk_idnr | bigint | not null default
nextval('dbmail_messageblk_idnr_seq'::regclass)
physmessage_id | bigint |
messageblk | bytea | not null
blocksize | bigint | not null default (0)::bigint
is_header | smallint | not null default (0)::smallint
Indexe:
»dbmail_messageblks_pkey« PRIMARY KEY, btree (messageblk_idnr)
»dbmail_messageblks_physmessage_is_header_idx« btree
(physmessage_id, is_header) CLUSTER
Fremdschlüssel-Constraints:
»dbmail_messageblks_physmessage_id_fkey« FOREIGN KEY
(physmessage_id) REFERENCES dbmail_physmessage(id) ON UPDATE CASCADE ON
DELETE CASCADE

And immediately after the drop I got this:
DELETE:ERROR: could not open relation with OID 102021
DELETE:CONTEXT: SQL statement "DELETE FROM ONLY
"public"."dbmail_messageblks" WHERE "physmessage_id" = $1"

for each and every delete of a row in that table. After a
REINDEX TABLE dbmail_messageblks;
everything seems to work.

Is that a bug or did I do something bad?

mfg zmi
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