If I start it then I always get an error: "soldierfront.exe has stopped working."
I tried to debug and find the error source but the only thing what I found is SF wont start anymore.

Unhandled exception at 0x779f6bd2 in soldierfront.exe: 0xC0000005: Access violation writing location 0x00030fe4.

I have figured out this one error. You have to open version.ini in the SF folder and change version from 528 to 500. After this the updater will download again the newest files and it will repair your client.