Asterisk Service Stops Frequently

I have asterisk 1.2.7.1 configured with TDM2400. I am running Asterisk in RedHat Enterprise Linux 3 operating system. Asterisk Service stops by itself (Once in a week), and then I need to start the service manually. Where do I find logs for these type service problem in asterisk server. Please help me resolve this issue.

Thanks
Krishna

/var/log/asterisk/… and why such an old version? 1.2.26.2 is current.