Invalid JSON string:0 error while trying to run Dashboard Reports.

We have recently upgraded from 11.1.1.5 to 11.1.1.6.12 and here is an interesting issue that we have faced when we tried to access the Dashboards and Reports.

We received the below dialog box from the webpage.

There might be several reasons for this error as i read in many places the possible reasons in my scenario are

1. The cache which is in my browser prior to upgrading is causing issue as it cannot find the related files with upgraded version.
2. Analytics server might not be deployed correctly.

But the solution that worked is clearing the browser cache and restarting the browser and then trying to load the BI dashboards.