Hello, I'm new to this game, and I am having the exact same problem. I tried joining servers with 4.02 in their names, but none worked, I kept getting the same error message of "Your map differs from the server's." I am sure I downloaded the beta 4 version. If it helps at all, when I try joining a server for the first time, it begins downloading the map as a .ain file, but when it shows the error message it displays a .bsp file. for example, I'll join a server, and it will say "downloading ge_cradle.ain," then it gives me the error message saying "Your map [/ge_cradle.bsp] differs from the server's."