When upgraded to HF10 in GS 5.2.1, the Dashboard stats show "loading..." and do not load the stats data.
The issue is caused due to prototype.js mistakenly removed in 521 hf10 from the following location.
datasynapse\manager\webapps\livecluster\admin\inc\scripts\prototype\prototype.js

The following workaround can be followed to remedy the issue.
Workaround :
(*) If the server is not yet started:

     - When the HF10(Tomcat only update) is installed, before starting the server:

     - Place prototype.js from datasynapse\manager\webapps\livecluster\WEB-INF\uninstall\5.2.1_hotfix10\manager\webapps\livecluster\admin\inc\scripts\prototype/prototype.js 
to datasynapse\manager\webapps\livecluster\admin\inc\scripts\prototype\prototype.js

     - Start the server

(*) If the server is already started:

     - Stop the Server

     - Place prototype.js from datasynapse\manager\webapps\livecluster\WEB-INF\uninstall\5.2.1_hotfix10\manager\webapps\livecluster\admin\inc\scripts\prototype/prototype.js to

datasynapse\manager\webapps\livecluster\admin\inc\scripts\prototype\prototype.js

     - Start the Server