You need to disable avast!'s self-defense module (in Troubleshooting). After that you should be able to delete the local folder. BTW, I also have this folder (with many pak files around 4 KB large) and I don’t think that it is the cause of your problems. Reinstalling seem to be the best choice, I guess.
I’m not sure if this could related to your system setting or not. You should check this.
Sorry, I have never use local language, so others may have better solution.