Hi Michael,
I am trying to help a customer troubleshoot a similar issue using Customer Modifier and Customer Combiner in GP 2010. I believe what the message is saying is that it is trying to put a varchar into a column that is set up as float, meaning you have a table with a CUSTNMBR column that is set up with a type of float.
Can you run the following script against your company database in SQL and see if any of the data types are anything other than char?
SELECT
TABLE_NAME, COLUMN_NAME, DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME in
(SELECT name
FROM sysobjects
WHERE xtype = 'U')
and COLUMN_NAME = 'CUSTNMBR'
ORDER BY COLUMN_NAME, TABLE_NAME