Your custom menu files should load though. If it detects a mismatch it means it trys to load yours but doesn't apply JK2MV's menu content because it can't safely do it.
Yeah, I realised that during that debugging session, thanks :P Maybe you could hide these hash mismatch messages from release build? It looked to me as if it was mine .menu file being rejected, even if it makes sense now.
Another, similar question. I'm in the process of adding a gametype and everything goes well until this little detail: on the createserver menu, ui module parses .arena files and matches gametype strings like "ffa", "ctf" in order to determine what maps are available for my gametype. Using strings rather than gametype numbers looks like pretty unfortunate choice to me, because you can't override them without changing the ui code. Even if you do, it won't work in the main menu of jk2mv.
I guess you were going to release the ui API (ie let jk2mv load external ui module in the main menu) with mvsdk? Version checking seems to be in place for doing it now, although the menu code isn't compatible with jk2mp.exe but this can be easily fixed.
I still think that adding a gametype shouldn't require modifying ui code (apis change and as history shows, unmaintained mods stay popular for years). Current architecture encourages replacing, rather than adding gametypes. How about adding backwards-compatible .arena format with numbers instead of strings? Or/and some sort of gametype "redirection" like in UI_MapCountByGameType, but defined in ui/jk2mp/gameinfo.txt? I can write a patch, but I'd rather ask first as I only had a quick glimpse of all these.
And finally, would you rather have such discussions here or on github issue tracker?