When trying to run from the command line (cmd) of some commands such as ping, nslookup, sfc, ipconfig, help … closes the command prompt. Through the Start-Run these commands are run and work successfully. Commands such as set, echo, dir, cd from the command line work successfully. Situation is observed in WinXPSP3.
Maybe Avast is considering a run programs from cmd as a virus and blocks?
Consistently shutting down the shields, I found that this is a Behavior Shield. When the Behavior Shield is stopped, commands run successfully. If uncheck the “Monitor the system for unauthorized modifications” in “Expert Settings” of Behavior Shield, commands run successfuly with running Behavior Shild.