vSphere 4.1 U3 reboots

Hello,

I have 2 Supermicro servers with vSphere 4.1 update 3 build 800380 installed with vmware-esx-drivers-net-ixgbe_400.3.9.13-1vmw.2.17.249663.697530 injected. The iso file was customized by ESXi-Customizer-v2.7.

The servers works very well except one thing. They reboots by themseves randomly. Let say one time a week. I was looking on the logs for any messages by I don't see anything usefull for me.

The file messages shows:

Feb 1 05:47:41 sfcb-CIMXML-Processor[1183833]: -#- HTTP header command is not expected

Feb 1 05:56:16 vmklogger: Successfully daemonized. - time when ESXi host start booting

Can anybody point me into right direction where do I have to dig, which logs I have to check to find the reason of crashes?

I have a bunch of logs, of course hard to read, but I would like to know which one shows the state of ESXi at that point of time. I mean not the logs between vCenter and ESXi host, but any logs like purple screen, driver crashes or hardware failure.

Thank you.