"No such file or directory" within /proc ?

Hi List, while doing a "du" in /proc, I get the following error msg: du: `./2220/fd/4': No such file or directory not quite sure, but doesnt "fd" mean a file descriptor? could it be an installed rootkit causing that error msg? Greeets Chr. Burri .-. /v\ L I N U X // \\ >I know KungFu!!< /( )\ ^^-^^