I will try out the rcon tools and simply take a look into the raw udp dump to clarify this a bit more.
Edit: Hm. With both programes I encounter some problems.
For example if I send say выыв in the console tab I always get question marks (????) in cod4.
So from this point I have no testing opportunity
@Mirko911: Any ideas? I think the main difference is, that with prior versions the config.cfg file was encoded with Windows-1251 (according to Notepad++). And now it is UTF-8. First quick and dirty tests were negative. I'll investigate it further tomorrow/next week.