[CentOS] Reseted net statistics

Hi all,

sometimes I´m checking status of my server with phpSysInfo, always is all right, but at May 8 I was experienced a "big deviation". My machine was online for 12 days, but net statistics are reseted. I was checked /proc/net/dev and there are reseted net statistics too. How is this possible?

Just before I was experienced this problem I was updating two packages with yum (perl-HTML-Parser.i386 3.56-5.el5 and epel-release.noarch 5-3). In /var/log/messages is nothing about it. At the same day someone attemped to log in to ssh (attack was about 10 hours long, but its impossible to break my server - I´m using private key allowed only from my IP and in AllowUsers is only root) so I don´t know, how is this possible.

Thank you for answers