Services fail to start up

We have a 4 CPU Wintel Box with 4 GB Memory. Inside we have WebAS 6.4 with 3 J2ee Instances.

All the instances were working ok, till this morning. When we restarted the server a number of the services did not get automatically started. We had to go into the config tool and start them manually.

Can anyone advise on what the problem might be and what the resolution is?

Also how/where can I ensure that the services are started (is there some property file etc)?

Thanks in advance,

Manik