Yohoo!
> 2011-01-04 10:10:37 host1: Can't fork at
> /usr/share/backuppc/lib/BackupPC/Lib.pm line 1128.
>
> All other hosts (with same OS) don't have this problem.
http://lmgtfy.com/?q=Linux+%22Can%27t+fork+at%22
Well, you might find some answers there. Without further information we
can't give any advice but I'd say you should check resources on this
server....
Christian