BizTalk Server 2006 R2 WSE Issue

I recently upgrade BizTalk Server 2004 to BizTalk Server 2006 R2 version. I successfully migrated and deployed the application. However, when I try to test out the application which calls web service using WSE adapter, I get the following error:

The Messaging Engine failed to create the transport adapter “WSE”.
OutboundAssemblyPath: “C:\Program Files\Microsoft BizTalk Server Adapter for WSE 2.0\Microsoft.BizTalk.Adapter.WSE.dll”
OutboundTypeName: “Microsoft.BizTalk.Adapter.WseTransmitter.WseTransmitter”
Exception Details: “Could not load file or assembly ‘file:///C:\Program Files\Microsoft BizTalk Server Adapter for WSE 2.0\Microsoft.BizTalk.Adapter.WSE.dll’ or one of its dependencies. The system cannot find the file specified.”

I installed BTSAdapterforWSE and SP1. Any ideas? Thanks in advance!