[Mailman-Users] list suddenly stopped working

[Christian Stalberg]

   I host several lists. One of them suddenly stopped working. In poking
   around I see that the ownership had changed from mailman to apache

   [root at zarathustra mailman]# ls -la /var/lib/mailman/lists/listdude
   total 56
   drwxrwsr-x.  2 root    mailman  4096 Jun  8 07:41 .
   drwxrwsr-x. 18 root    mailman  4096 Feb 19 19:21 ..
   -rw-rw----.  1 apache  mailman 18639 Jun  8 07:41 config.pck
   -rw-rw----.  1 apache  mailman 18639 Jun  8 07:41 config.pck.last
   -rw-rw----.  1 mailman mailman   132 May 14 14:26 pending.pck
   -rw-rw-r--.  1 apache  mailman    20 Jun  8 07:41 request.pck

   first of all, how could this occur? secondly, I changed the ownership
   back to mailman but the list still does not work. what should I do next
   please?