Summary

When on the view issue screen, if you click on an active sprint name, then it brings up a broken modal dialog. This only happens when using a version of JIRA less than 6.3, for example 6.2.4.

Steps to replicate

1. Install a fresh JIRA 6.2.3.
2. Install JIRA Agile 6.3.12.
3. Go to Agile > Getting Started.
4. Click on the create a sample project link (Scrum).
5. Once the new project has been created, browse to an issue which is in an active sprint (e.g. SSP-10).
6. Click on the link to the active sprint:
   
7. A pop up will open and the loading wheel keeps spinning forever.
   

The link to the active sprint on issue SSP used in the example is:
http://yourjira:8765/dconrad-jira623/secure/GHGoToBoard.jspa?sprintId=2

Right-clicking the link and opening it in a new tab works fine.

Workaround

Upgrade JIRA to 6.3 or above.