This week Comodo stepped on a rake. They released a new virus database and cmdagent.exe service went completely crazy: it took about 100% of CPU time and made computers totally useless.
The cure was to start computer is Safe mode (press F8 during boot) and copy the installation default virus database bases.cav from
C:\Program Files\COMODO\COMODO Internet Security\repair
to the working directory
C:\Program Files\COMODO\COMODO Internet Security\scanners
then update the database again to the corrected new version.
Comodo had the problem rectified pretty quickly but still those who got into the trouble had to apply the fix manually. Hopefully it was the last time when Comodo accidentally released not completely tested update and they will be more careful in the future.