ohadinho -
Please help me understand the problem you are having; are you saying that your project worked until you added the Couchbase.dll and Enyim.Caching.dll to the GAC?
Do you have a requirement for GAC deployment?If you can avoid the GAC, I would!
Also, can you look deeper into the stacktrace and find where and what is causing the type initializer error?
Thanks,
Jeff