Connection permissions

Hello,

I'm problamas permission in my application, I do upload a spreadsheet (xlsx.) To a directory on the server, when I try to connect to it via OleDB get the following message:

System.Data.OleDb.OleDbException 
ErrorCode: -2147467259 
Message: Unspecified error 

Erros List 
Message: Unspecified error 
NativeError: 0 
Source: Microsoft Access Database Engine 
SQLState: 

My authentication mode is via Form and imporsonate "true".

I thought this article http://support.microsoft.com/default.aspx?scid=kb;EN-US;825738 who can help.
All testing I have done, I found that the problem is permission. Does anyone know where and what folder I should set user permissions?