PostgreSQL - NPgsql

saludos a todos de lawebdelprogramador

intento conectar postgres(bajo windows la 8.3) con un manejador de contenidos(Dotnetnuke version 4.07)... al utilizar la NPgsql.dll... que se necesita para poder interactuar con VWD express... al cargar el sitio me sale el siguiente error

Could not load file or assembly 'Npgsql, Version=1.98.2.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.IO.FileLoadException: Could not load file or assembly 'Npgsql, Version=1.98.2.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Assembly Load Trace: The following information can be helpful to determine why the assembly 'Npgsql, Version=1.98.2.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7' could not be loaded.

AVS: El registro del enlace de ensamblado está desactivado.
Para habilitar el registro de errores del enlace de ensamblado, establezca el valor de Registro [HKLMSoftwareMicrosoftFusion!EnableLog] (DWORD) como 1.
Nota: existe una disminución del rendimiento asociada registro de errores del enlace de ensamblado.
Para desactivar esta característica, elimine el valor de Registro [HKLMSoftwareMicrosoftFusion!EnableLog].

Stack Trace:

[FileLoadException: Could not load file or assembly 'Npgsql, Version=1.98.2.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)]
DotNetNuke.PostgreSqlDataProvider.PostgreSqlHelper.ExecuteReader(String connectionString, String spName, Object[] parameterValues) +0
DotNetNuke.Data.PostgreSqlDataProvider.GetPortalAliasByPortalID(Int32 PortalID) +77
DotNetNuke.Entities.Portals.PortalAliasController.GetPortalAliasByPortalID(Int32 PortalID) +35
DotNetNuke.Entities.Portals.PortalSettings.GetPortalAliasLookup() +74
DotNetNuke.Entities.Portals.PortalSettings.GetPortalAliasInfo(String PortalAlias) +14
DotNetNuke.HttpModules.UrlRewriteModule.RewriteUrl(HttpApplication app) +3535
DotNetNuke.HttpModules.UrlRewriteModule.OnBeginRequest(Object s, EventArgs e) +837
System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +138
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +65

probe con remover [HKLMSoftwareMicrosoftFusion!EnableLog].. pero no me funciona

si me pueden ayudar

de antemano gracias

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Version Information: Microsoft .NET Framework Version:2.0.50727.42; ASP.NET Version:2.0.50727.42