Strange error: membershipCreateStatus is ambiguous in 'system.web.security'

I'm getting a strange error.  I am reconstructing my site on my local PC after a virus, and when I compile, I get the message:
membershipCreateStatus is ambiguous in 'system.web.security'
I did notice as I compiled that a message came up about nuget package being reconstructed.
   I also notice dlls with .refresh added in my bin folder:
 Microsoft.Data.Edm.dll   Microsoft.Data.Edm.dll.refresh   Microsoft.Data.Edm.xml   Microsoft.Data.OData.dll   Microsoft.Data.OData.dll.refresh   Microsoft.Data.OData.xml   Microsoft.Data.Services.Client.dll   Microsoft.Data.Services.Client.dll.refresh   Microsoft.Data.Services.Client.xml   Microsoft.Practices.TransientFaultHandling.Core.dll   Microsoft.Practices.TransientFaultHandling.Core.dll.refresh   Microsoft ...