Hi,
In my scenario, We have SAP BO 4.1 SP4 Patch 3.
When we have upgraded JAVA 8 then same error was given when i tried to open web intelligence reports. Even after minimize security level, it was not getting resolved then we have removed JAVA upgraded version 8 and problem has been resolved.
Might be you faced similar issue, in this case, you have to removed JAVA upgraded version.
Regards,
Dhaval Dave