REP-1401: 'cf_weight_uomformula': Fatal PL/SQL error occurred.

 A customized Invoice Printout Report completes with an ERROR:

MSG-00010: AND 1=1 AND rctt.type = :p_transaction_class  AND rct.trx_number >= :p_trx_number_low  AND rct.trx_number <= :p_trx_number_high  AND rct.trx_date >= :p_dates_low  AND rct.trx_date <= :p_dates_high
MSG-00000: Cust TRX ID : 537881
MSG-00000: EFTA Country: DE
MSG-00000: EFTA Language: D
REP-1401: 'cf_weight_uomformula': Fatal PL/SQL error occurred.
ORA-01722: invalid number

Any Idea what that means? Where should I look for a solution?  I can not find such an error in Metalink.

Thanks

Dimitri