Symptoms

I have created one simple smart object to update the data for one table in SQL. My store procedure works completely fine when I ran from SQL. I created Smart Object for same using Smart Object Tester Utility. The Smart Object was created successfully but as soon as I execute the Smart Object with Values I get error for "Nullable object must have a value".
 

Diagnoses

The stored proc was using an unsupported "Numeric" type. Please see the documentation below regarding SQL data types that are not supported:

AutoNumber
AutoGuid
TimeStamp
Image
SQL_Variant
Binary
VarBinary
Numeric
Hierarchyid

http://help.k2.com/onlinehelp/k2blackpearl/userguide/current/webframe.html_ws_sql_01.html
 

Resolution

After changing the data type and assigning default values in the stored proc, it is now working as intended.