Object Reference error

I've customized the nop cart and added up some classes into the Nop.Common, Nop.DataAccess and Nop.DataAccess.SQLServer.

the problem is with the DBxxxxxProvider class, it is giving me the error 'Object Reference not set to an instance of object' when it goes to Initialize() and check for

                if (s_InitializeException != null)
                {
                    throw s_InitializeException;
                }

Have you added appropriate sections to your web.config file?

<section name="xxxxxProvider" type="NopSolutions.NopCommerce.DataAccess.xxxxx.DBxxxxxProviderSection, Nop.DataAccess" requirePermission="false" />

and

<xxxxxProvider defaultProvider="SQLxxxxxProvider">
      <providers>
        <add name="SQLxxxxxProvider" type="NopSolutions.NopCommerce.DataAccess.xxxxx.SQLxxxxxProvider, Nop.DataAccess.SqlServer"  connectionStringName="NopSqlConnection" />
      </providers>
</xxxxxProvider>

hurray! it works,

Thanks a lot for quick reply and for support,

When I tried to re-build all components at VS2008, I got the following error:

Error  The name 'lblOrderNumber' does not exist in the current context  .....\Modules\CheckoutCompleted.ascx.cs  59  

Has anyone got this error before?  What if I just simply commented this line of code out?