Are you talking about the 'Message Filters' filter log ? Have you created any Message Filters for an account? Are they enabled ? If yes, do you know they work because incoming mail gets auto filtered into relevant folders ?

In Message Filters window Make sure you have selected an account which has some filters you created. When you click on 'Filter log' it should open in a new window - does that occur ? Is the checkbox 'Enable the filter log' selected? If no then select it.

Please report back with info.

I've enabled the log but can't view it