I just upgraded my site from 4.4.0 to 4.6.2 and the upgrade completed fine.  I can bring up the site and everything is there and working except when I try and login.  When I hit the login button I get A critical error has occurred.

I checked the web.config and the add name="Authentication" type="DotNetNuke.HttpModules.AuthenticationModule, DotNetNuke.HttpModules.Authentication" /-->

is commented out so if I up comment it then I get

Configuration Error
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: Could not load file or assembly 'DotNetNuke.HttpModules.Authentication' or one of its dependencies. The system cannot find the file specified. (E:\intranet2\web.config line 55)

Source Error:

Line 53:     <!-- HttpModules for Common Functionality -->
Line 54:     <httpModules>
Line 55:       <add name="Authentication" type="DotNetNuke.HttpModules.AuthenticationModule, DotNetNuke.HttpModules.Authentication" />
Line 56:       <add name="Compression" type="DotNetNuke.HttpModules.Compression.CompressionModule, DotNetNuke.HttpModules" />
Line 57:       <add name="RequestFilter" type="DotNetNuke.HttpModules.RequestFilter.RequestFilterModule, DotNetNuke.HttpModules" />
 
any help would be great

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Thanks for your help I did the upgrade and I get the same error.

Well in this case either to roll back to the first version you have (if you do have backup) or you may contact your dev to fix this for you. Hopefully someone here can know whats going wrong

Regards,
andy