My SP 2010 setup is two separate applications - one for the main portal and one for MySite. Whilst WebAnalytics is tracking usage of MySite it's not showing any stats for the main Portal. The only thing it lists is the number of site collections but no page views etc.

The WA service is clearly running to pick up data for MySite. In Configure web analytics and health data collection everything is ticked. I can't find any obvious settings that are different between the two applications.

Where should I look to get usage tracking correctly?

Edit:

Having played with the date ranges I see that actually I've got no stats in the last 7 days for any site at all including MySite which has been working at some point previously.

Edit:

What does each service (WA Data Processing Service vs WA Web Services) do and where should they be active? At present they're both running on an App server but not on the WFEs (although they were running on WFEs previously). From what I can gather than only need to run on an App server but I find it strange that the only logged activity I see in the staging database relates to Central Admin URLs on the App server and nothing from the WFEs.