Did you try ask the server you are playing what is the problem? Gepard is an anti-hack thing servers use so the server might be able to give you a better comment from the log.
With the language issue, I recommend you download the full client of the server you are trying to play and install it to a new folder. This might solve your crash problem too. Your client is not reading any language file other than the default ones (that is likely in Korean).
