Samba Amavis just stopped working

Hi to all, I experienced a few strange behaviors at our server in the last time. I installed Suse 9.1 and everything worked fine untill a few days. I noticed one time that I don't receive emails and after that I saw that Amavis was down. I mean the process was not running. I looked all over in the logs to find a clue but didn't see anything strange. Today the same happened with samba. The service has just stopped. I also looked in the logs and nothing. With amavis it happened once 2 times a day, with samba only one time, but I see it very strange. Does anyone has a clue??? Any info is welcomed. PS: we have a small network so I excluded the posibility that a user could do it manually. Thank you. Andy.