[syslog-ng]dns_cache problems with v1.5.13

hi all, im currently using syslog-ng version 1.5.13. i have experienced problems where negatively cached records were preserved indefinitely. only a full restart would cause these ips to be resolved, even a hup would fail. i've now turned off caching cos we rely on ips being resolved in these log files. impt part of the config attached, thanks, colm -- options { sync(0); log_fifo_size(1000); use_dns(yes); dns_cache(yes); use_fqdn(yes); chain_hostnames(no); };