FTP - ScoreboardFile, Operation not permitted

[rviradia]

I started getting this out of the blue (ftp stopped working with message "Control connection closed."), so I commented it out and ftp works now, but what caused it?

proftpd[13542]: Fatal: ScoreboardFile: : unable to use '/var/run/proftpd/scoreboard': Operation not permitted on line 43 of '/etc/proftpd.conf'

Thanks in advance