SSRS 2012 Charts not rendering

Hi,

We recently upgraded from SQL 2008 R2 to SQL 2012, and since then, all of the charts in our reports will not render.  They appear on the report server with a red "x".  When running the reports in report builder, the charts do not show at all.   However, the charts DO render when the page layout mode is toggled.

Any help on this issue is greatly appreciated.

Thanks,
Mike