it does exist and that's where I edited the sound, but now it's in the original state.
I might be a bit late but just regarding this pat of the issue:
client_default.cfg is the default configuration and not supposed to be edited.
If you want to change the settings try client.cfg instead (if a setting doesn't exist just copy it from the default)
I can't really help you regarding your general problem as I usually play on a windows machine...
but: since you have a 64bit system it might be that some libraries are 64bit and needed as 32bit (or the other way around after your switch to the 64bit client)
In addition to that:
Who is the owner of the client_default.cfg and what rights are set for it? (on command line go to the directory and do "ls -l", of course without the quotes, to get the full list)
Is it the same as your user or another one?