Error number -119 character in CAST argument is invalid, and DMS-E-INVALIDNULL

Problem

Descri[ption: After upgrading a report from Impromptu 7.0 to 7.3, receiving two error messages: Error number -119 character in CAST argument is invalid, and DMS-E-INVALIDNULL. There are also cast conversions in the SQL that were not present in version 7.0. Environment: Win2000, Impromptu 7.3.648, DB2/400 on V5R2 via iseries access express V5R2 Error Message - Error number -119: DMS-I-INFORMATION, The target database has returned information concerning the 'fetch' operation. [IMB][iSeries Acess ODBC Driver][DB2 UDB]SQL0420 - Character in CAST argument not valid. DMS-E-INVALIDNULL, The database returned a NULL value for a column previously described as not nullable. Solution: Examine the calculation in the report, looking specifically for nested conversions around a calculation, of the form:

number-to-string ( string-to-number (number-to-string ( numericfield ) + stringfield + '01' ) )

number-to-string ( numericfield ) + stringfield + '01'