cannot open server.properties - HTTP Status 404 /arcgis/rest: The requested resource (/arcgis/rest/) is not available

I recently faced this issue in ArcGIS Server Java 931.  I have installed server 931 and tested the REST services, it was working fine.

But the next day, i am not sure what happened or change in the server machine.  If I hit the
http://hostname:8399/arcgis/rest/services

It is showing "Not available".. in the error log (..prgfiles/arcgis/..java/../log), it shows the following error as Sever
e "cannot open server.properties".

I tried all the suggestions given in the ESRI site, nothing working.. Finally, I did post install once again, now it is working.