Hello,
If you have multiple WFE servers you need to do the same (iisreset) on each server.
Also please ensure that you run Configuration Editor tool on each WFE server and all requirements are in green.
Check your WFE server for any reference to the version 2.0.0.0 of the above assembly and remove it manually (before you do that please backup the file).
Use ULSViewer and localize exactly the exception logged in there when the above error happens.