Hello,
What version of SEPM are you running?
Here are the Steps I would suggest you to perform -
1) Remove the Proxy settings.
2) Restarted the SEPM Services .
3) Restore the Proxy Settings .
4) Pie chart was working fine & showing the correct data.
and
I would recommend you to Migrate to the Latest version of SEP 12.1 RU2
Secondly, this Article which speaks of Exact same issue:
In the SEPM home page, the Symantec Security Response panel does not open, it displays: "This program cannot display the webpage"
http://www.symantec.com/docs/TECH186802
Hope that helps!!