One of the nice features in TFS2010 are the Excel Agile Planning Workbooks. One part that I have had some problems with is the burndown chart where I would get an error "the iteration dates are not valid" and recommending that I go the settings tab to make a change.
For a long time, I just assumed that it was due to the fact that I tend to install lots of stuff on my machines. Today, in prep for my session tomorrow, I decided to investigate this – and it turns out there is a knowledge base article on this issue. In my case I was running SQL 2008 R2 (which does not come with TFS 2010, TFS comes with SQL2008), and the problem occurs with R2. The KB article describes the problem and the really simple resolution – where I simply needed to update a config file and restart the service. My burndown chart is now working quite nicely
Lesson of the day – KB articles can be really useful!