Interfacing with MSAccess

Exporting tables from Access to PG using ODBC driver Greatbridge 1.00.0000.
Function in PG to check data validity:

CREATE FUNCTION my_MonthlyPayment (NUMERIC, NUMERIC, INTEGER)
 RETURNS NUMERIC
 -- Returns monthly payment for  $1: loan
 --    $2: annual interest rate, in %
 --    $3: number of months
 AS
 '
  SELECT CASE
   WHEN $2 :: float = 0.00 THEN
    ($1 :: float / $3)
    :: NUMERIC(7,2)
   ELSE
    ($1 :: float * $2 :: float / 1200.00 *
    (1.00 + $2 :: float / 1200.00) ^ $3 :: float /
    ((1.00 + $2 :: float / 1200.00) ^ $3 :: float - 1.00))
    :: NUMERIC(7,2)
  END
;'
 LANGUAGE 'sql';

After some processing (query progress indicator at half) the following error
message pops up:

Error while executing the query(non-fatal);
ERROR: fmgr_info: function 1350878: cache lookup failed (#-1)

Please help.