SSRS 2008 Report Viewer in Sharepoint -Expanding a column in matrix pushes numbers off the report

I am using SSRS 2008 in integrated mode on a WSS 3.0 site.  I have a report with a matrix in it.  THere are two columns (Project/task).  When I expand the project column (clicking +), the tasks will show up.   Everything works
fine in BIDS.  But when I try to view the same report in WSS, the numbers in the columns beyond task get pushed over by 1 column whenver I expand the project column.  

For example, this is what the report looks like before I expand the project column –

Project              MTD    YTD
+ProjectA           100    200
+ProjectB           300    400

After I click +, I get

Project              MTD    YTD
+ProjectA       Task 1     10    20
                      Task 2    90    180
+ProjectB           300    400

Does anyone know how to fix this?

Thanks.