In the last two weeks Nagwin has been creating 16 GB daily log files. I don't see any configuration changes in any files for that day. Previously they had been 10-1000 KBs.
It looks like the default settings are being used in the nagios.cfg. One thing I noticed was the debug was set to 147 (which doesn't look like a valid setting as I don't believe you can have a 1, 4 and 7 for debug set at the same time in a string?)