OK, I got it to work. The 2010 schema has changed. You can use the SQL Server Mgmgt Studio to access the metadata and query the tables.
For the Task Burndown chart, here's the command that worked in a browser:
http://{your tfs sql svr rpt server}/Reports/Pages/Report.aspx?ItemPath=%2fTfsReports%2fDefaultCollection%2fCcMsd1.0%2fDashboards%2fBurndown&rc%3atoolbar=false&rs%3aCommand=Render&IterationParam=[IterationName].[ParentIterationSK].%26[17]
Here's the comand that worked in the project portal web part:
/sites/DefaultCollection/CcMsd1.0/_layouts/TfsRedirect.aspx?tf:Type=Report&tf:ReportName=Dashboards%2fBurndown&tf:ShowToolbar=0&Width=381pt&Height=180pt&tf:Command=Render&tf:Parameters=IterationParam=[IterationName].[ParentIterationSK].%26[17]
I will be posting this and more of my work on team portal/web part customization on
http://agilescmtalk.com/Bob
Bob Hardister