You are getting this error because of the calculated column. Here is the error explained in a KB article:

http://support.microsoft.com/default.aspx?scid=kb;en-us;Q316146

Microsofts says a fix is in the works. In the mean time, check out the following Knowledge Base articles that work around it in 3 different ways:

This helper class copies rows from multiple DataTable objects into a 3rd
DataTable.

Q325688 HOW TO: Implement a DataSet JOIN Helper Class in VB .NET
http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q325688

This article has a class that's a fairly full-featured replacement for the DataView.

Q325682 HOWTO: Implement a Custom DataView Class in VB .NET
http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q325682

This article extends part of the DataGrid to pull data from another DataTable.

Q319082 HOWTO: Extend Windows Form DataGridTextBoxColumn to Display Data
http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q319082



>Hi, all...
>
>I'm getting a .NET exception error, 'no proposed data to access'...
>
>It's occuring when I'm trying to modify the contents of a row...
>
>The row/table I'm trying to modify is not readonly, and I'm wrapping the changes around a 'beginedit, endedit, acceptchanges' block of code. I've even typed in code from on-line help, but I continue to get the 'no proposed data' error....
>
>Basically, I'm just trying to set some string columns to specific values for a certain row.
>
>Any clues?
>Thanks,
>Kevin