I finally managed to make it work. The problem was on the version of some dlls used by Couchbase.NetClient.dll. The error was misleading. As soon as i manually changed the versions to web.config (to the newer ones) it worked.
I tried to make also a version of ASP.Net Output caching with no luck since now. Seems this bug has to be fixed first but i will try further (RawBinaryTranscoder problem). LegacyTranscoder does not seems to do the job.