If you run into trouble with PRTG Traffic Grapher here are some tips to help you find the cause of the problem:

Check the log files

PRTG Traffic Grapher creates two log files:

• "PRTG Traffic Grapher Logfile (application).log"
  is written while the program runs in GUI mode
• "PRTG Traffic Grapher Logfile (service).log"
  is written while the program runs as a service

Both files are stored in the folder where the INI file is stored, usually:

C:\Documents and Settings\All Users\Documents\
     PRTG Traffic Grapher\*.log

While using PRTG in GUI mode you can view the files using the menu item Help|View Logfiles.

Check the System Event Log

In some situations PRTG also writes a message into the application event log, e.g. if the disk drive is full and PRTG stops the monitoring process to avoid a crash.