[CentOS] Strange reboots

Hi,

I have a CentOS 5.0 running as a web server.

# uname -a Linux hostnamehidden.net 2.6.18-53.1.14.el5 #1 SMP Wed Mar 5 11:37:38 EST 2008 x86_64 x86_64 x86_64 GNU/Linux

Every 59 minutes (maybe every hour) it reboots without any logs, without any traces and unfortunately with breaking software raid. After reboot dmesg does not have any strange entries.

I double-checked crons, any strange services, nothing suspicious.

I did "yum update" recently.

I went to Datacenter and waited before the monitor but during reboot I did not see anything strange. I guess reboot is cold reboot.

I changed all system and cpu fans. Upgraded system powersupply with a more powerful one. Placed server infront of air-conditioner.

Do you have any idea?

Thanks.