Q: SQL Server Import Wizard treats NULL as literal string 'NULL' When I attempt to import a .csv comma-delimited flat file into a Microsoft SQL server 2008R2 64-bit instance, for string columns a NULL in the original data becomes a literal string "NULL" and in a numeric column I receive an import error. Can anyone please help??? 

A: Put the data into a staging table and then insert to the production table using SQL code.
update table1
set field1 = NULL
where field1 = 'null'

Or if you want to do a lot of fields
update table1
    set field1 = case when field1 = 'null' then Null else Field1 End
      , field2 = case when field2 = 'null' then Null else Field2 End
      , field3 = case when field3 = 'null' then Null else Field3 End


A: KISS
Pre-process it, Replace all "NULL" with "".
ie the .csv file will have
,,

Instead of 
NULL,NULL,

Seems to do the job for me.

A: Adding to HLGEM's answer, I do it dynamically, I load into staging table here all column types are VARCHAR and then do:
DECLARE @sql VARCHAR(MAX) = '';
SELECT @sql = CONCAT(@sql, '
    UPDATE [staging].[',[TABLE_NAME],']
    SET [',[COLUMN_NAME],'] = NULL
    WHERE [',[COLUMN_NAME],'] = ''NULL'';
    ')
FROM INFORMATION_SCHEMA.COLUMNS
WHERE [TABLE_SCHEMA] = 'staging' 
    AND [TABLE_NAME] IN ('MyTableName');
SELECT @sql;
EXEC(@sql);

Then do:
INSERT INTO [dbo].[MyTableName] ([col1], [col2], [colN])
SELECT [col1], [col2], [colN]
FROM [staging].[MyTableName]

Where table [dbo].[MyTableName] is defined with the desired column types, this also fails and tells you in type conversion errors...
