There is no way to solve the problem because this isn't really a problem: you can go into the mods section of the menu and run again standard OA (baseoa), it should bring back the blue menu.
What about the new statistics feature? Are the kills, frags, etc. are counted, when the mod is not loaded and is the menu only not accesible, or do i need to (re-)load the mod every time i leave an arena to get the statistics be written?
First case, stats are only counted if you play with the right mod (openarena) so when you join a server which uses another mod's QVM (like 0.8.1 servers, or mods like CPMA, Defrag...) they don't count anymore.
Fortunately rare are the servers who run mods which change the QVM, the actual problem is older 0.8.1 server which haven't stats.