Reading Data from Excel with all column filled gives error

Hi,
I am using ADO.NET. And JET 4.0 provider to read the data form
excel 8.0. Excel 8.0 have column limit as 255.
means A1 to IV. But when i fill all column with data including last IV
and try to read then it gives error that
"Too long field defined."All my cell have one or two character
record. But if i delete the last column IV record then it works
properly. can you give me information why it is happening.

Thanks
Neeraj Kumar