If DynamIPS (the DynamIP NT Service) starts DynamIP without DynamIP reading the appropriate settings from the INI file you should verify the following:

If DynamIP is started as an NT Service it will always read the settings from the file DynamIPS.INI in the directory from which you installed the DynamIP NT Service. If there is no such file DynamIP starts with default settings.
For example, if you installed DynamIP into the default directory C:\Program Files\DynamIP\ and then installed the DynamIP NT Service from the same directory, DynamIP reads the settings from the file DynamIPS.INI in this directory whenever it is started as an NT Service.

More information on this issue is available here.

Other NT Service Problems: