Shadow and Passwd empty after ISPConfig activity

[cryptic]

CentOS 5.2, ISPConfig 2.2.29

This morning one of my servers was not responding to services such as postfix and sshd. I had to reboot the server into single user mode. My passwd and shadow files only had entries to one site. Activity in my ISPConfig log correlates to the time that the system stopped responding. Also the entries in the log were for only the users that in my shadow and passwd file at the time of the issue. I restored my passwd and shadow files from a backup to fix the issue. This is the second time this has happened. This happened to me last year on a ISPConfig 2.2.24 system.

I've attached my ispconfig.log

[till]

Please check your passwd and shadow and group files with the commands:

pwck
grpck

[cryptic]

'pwck' returned some invalid user name's and asked me if I wanted to delete one line.