[syslog-ng]Some device doesn't write to file

Hi, I just upgrade the hardware and software of the syslog-ng server to 1.60rc4 from 1.5 to log about 30 firewalls syslog. After upgarde, I did find that nearly half of the firewalls log doesn't write to the file. I did check with tcpdump and it did receive the tons of logs but did't log into the file. The iptables/ipchains has all been disabled. Is there any way to identify the source of problem. Thanks for your help. B. Regards, Santa