DB-LIBRARY error

Hi,
I'm trying to execute a user defined scalar valued function.

the SQL for it is
select MyDatabaseName.dbo.UserDefinedFunction('parameter1','parameter2')
go

This results in the following return when using fisql.

DB-LIBRARY error:
        Data conversion resulted in overflow
Operating-system error:
        Successful



(1 row affected)


The return for the user defined function is an integer. I also tried another UDF where the return is a float. 
Same problem.

Anyone know what this could be?

Thanks.

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