Out of Memory - Clustered Chart rendering issue with number of columns in 2008R2, not in 2008

Getting old favourite message 'Out of Memory' when running a horizontal clustered chart with Category: 200 items Series: 200 items per Category.

We've read numerous previous posts e.g. http://ift.tt/1zApn07 which states that 'By default, the report server sets WorkingSetMaximum to the amount of available memory on the computer. This value is detected when the service starts.' 

The report has been tried on 3 large servers with 30GB & 60GB memory.

The report runs on a 2008 install but not a 2008R2 install. We've created a test report that simply generates a series of data 1-n for Category and 1-n for Series where n can be set by parameter - so the issue is not to do with the volume of data or the processing required by SSMS.

The report runs if the data is output to a table rather than a chart - so the issue appears to be with rendering the chart.

The chart is rendered when the Categroy has 200 items with a Series of 150 per Category. The report fails whith Category 200 items and Series 200 per Category.

The test report can be uploaded to this site if a MS representative or interested user is willing to help.

Thanks

Steve