Make sure log level is correctly set under dispatcher module:
<IfModule disp_apache2.c>
# location of the configuration file. eg: 'conf/dispatcher.any'
DispatcherConfig conf/dispatcher.any
# location of the dispatcher log file. eg: 'logs/dispatcher.log'
DispatcherLog logs/dispatcher.log
# log level for the dispatcher log
# 0 Errors
# 1 Warnings
# 2 Infos
# 3 Debug
DispatcherLogLevel 3
</IfModule>
Also check, loglevel under virtual host config, for example:
LogLevel info rewrite:info