R5 Client "Cannot find path to server" R8 Domino

We are still in an R5 enviroment getting ready to test our apps on an 8.0.2 server. I cannot access the server at all, my developer can access the server, but gets an encryption error. Is this due to the R8 server ID not being registered as backwards compatible to R5?

Thanks

Subject: I think there is a problem with the lengths of the key or so.