WCF Method not found only effects SOAP services

I thought I was going to have to blow the OS away on my laptop since it's the only computer I've got that is experiencing this error with SOAP services (REST works great):

The problem:
Method not found: 'Void System.IdentityModel.Selectors.SecurityTokenRequirement.set_IsOptionalToken(Boolean)'.


Stack trace:
at System.ServiceModel.Security.SecurityProtocol.AddSupportingTokenProviders(SupportingTokenParameters supportingTokenParameters, Boolean isOptional, IList`1 providerSpecList)
at System.ServiceModel.Security.SecurityProtocol.OnOpen(TimeSpan timeout)
at System.ServiceModel.Security.WrapperSecurityCommunicationObject.OnOpen(TimeSpan timeout)
at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)
at System.ServiceModel.Channels.SecurityChannelFactory`1.ClientSecurityChannel`1.OnOpen(TimeSpan timeout)
at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannel.OnOpen(TimeSpan timeout)
at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannel.CallOpenOnce.System.ServiceModel.Channels.ServiceChannel.ICallOnce.Call(ServiceChannel channel, TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannel.CallOnceManager.CallOnce(TimeSpan timeout, CallOnceManager cascade)
at System.ServiceModel.Channels.ServiceChannel.EnsureOpened(TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs)
at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)

The solution:
KB976394 - WCF: Make OutgoingSupportingToken public

Reference:

• http://support.microsoft.com/kb/976394
• http://blog.tinyshed.net/tinyshed/post/2010/06/28/Fix-SystemIdentityModelSelectorsSecurityTokenRequirementget_IsOptionalToken().aspx