Are you using separate code for the client and server or are you using the same code with IFDEF in them?

Point is that you have to be aware that the strings are indexed and have to be in the same place on both client and server. So if you define a new string on the client that the server doesn't know about, you will not get through.

Put all your variable and string definitions on the top of your code before you do anything else. This will make sure that you have those defined on both client and server and that they are properly indexed.