This error was a real nightmare for me where I'm being in middle of a migration process of our legacy system. Though there was real hits when you google this problem, but nothing was helpfull for me.
The context of the problem occurs when I did run it on a WinXP pro sp3+ workstation which had installed the latest ODP.NET. However its quite extraordinary to see it was not reproduced in a machine installed Oracle Express Edition 11g (without oracle client).
Later, I understood that this problems occurs if you have a VarChar2 parameter(s) when executing a Oracle Stored Procedure. So people advised to have the size and Parameter direction in the parameter. I incresed the size everytime of the parameter and had the parameter direction as "input", yet this error kept bugging me. (My stored procedures did not have any return/output parameters, so I'm not in a possition to comment its behavior).
Finally after googling for days and finding one post in the Oracle forum from one guy who said to use the direction as "InputOutput" did the work for me. Furthermore to the parameter direction, I also gave all of the VarChar2 parameter size as 2000.
Produced Environment: .NET framework 2.0, Win XP Pro sp3 and the latest ODP.NET
