int8 foreign key in Access subform yields ODBC error on NewRecord

Postgres table "item" has int8 primary key "item_id".

Postgres table "image" has int8 foreign key "item" referencing
"item"->"item_id".

Table "item" is represented on an Access form "item".

The form has a subform for the records in "image."

If form is opened with an empty "item" table, or if table is populated and
"New Record" button is pressed, error dialog "Error: ODBC call failed"
appears.

PsqlODBC log is attached. Here are the pertinent lines:

conn=47268416, query='SELECT "Item"."image_id" FROM "image" "Item" WHERE (
'' = "item" ) '
ERROR from backend during send_query: 'ERROR: Bad int8 external
representation ""'
STATEMENT ERROR: func=SC_execute, desc='', errnum=7, errmsg='Error while
executing the query'
-----------------------------------------------------------
-
hdbc=47268416, stmt=48423424, result=48423120
manual_result=0, prepare=0, internal=0
bindings=0, bindings_allocated=0
parameters=48423312, parameters_allocated=1
statement_type=0, statement='SELECT "Item"."image_id" FROM
"image" "Item" WHERE ( ? = "item" ) '
stmt_with_params='SELECT "Item"."image_id" FROM "image"
"Item" WHERE ( '' = "item" ) '
data_at_exec=-1, current_exec_param=-1, put_data=0
currTuple=-1, current_col=-1, lobj_fd=-1
maxRows=0, rowset_size=1, keyset_size=0, cursor_type=0,
scroll_concurrency=1
cursor_name='SQL_CUR02E2E200'
----------------QResult
Info -------------------------------
fields=48423088, manual_tuples=0, backend_tuples=0,
tupleField=0, conn=0
fetch_count=0, fcount=0, num_fields=0, cursor='(NULL)'
message='ERROR: Bad int8 external representation ""',
command='(NULL)', notice='(NULL)'
status=7, inTuples=0
CONN ERROR: func=SC_execute, desc='', errnum=110, errmsg='ERROR: Bad int8
external representation ""'

PostgreSQL 7.2.1
PsqlODBC 7.02.0001
odbc32.dll 3.520.9001.0
Access 97 SR-2
Windows 98 SE