If you see the warning WARNING: Your ClamAV installation is OUTDATED! - this sounds more dramatic than it actually is, and it is usually not necessary to take any action. This just means that a newer ClamAV version is available than the one that is installed - your current version is still ok. It does not mean that the virus signature database is not up to date - it actually is, and protection is still guaranteed.
About second problem: I have postfix and Mandriva 2010.1 64 bit, from last 3 days i have problems with 2 mail accounts in 2 different mail server on my server.Not eny changes in postfix files. My postfix server is realized by recommendation of "Perfect server Mandriva 2010.1 64-bit". I have not any problems to this moment.
Any errors in your mail log?