I\'m reading an Excel file with OLDB Connection using this code
var connectionString = string.Format(\"Provider=Microsoft.Jet.OLEDB.4.0; data source={0};
I had this exact problem and solve it with using IMEX setting. In case others are wondering how to include the IMEX, here is what I have on my connection string
string connectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Extended Properties='Excel 8.0;IMEX=1';Data Source={0};";
connectionString = string.Format(connectionString, excelWorkbookPath);