[Update 26th March 2014]
Fixed an issue with downloading data from NSE after their site layout redesign.
If you are an options oracle user and you are getting one of these weird error with Options Oracle as soon as you launch it, Error Message: "Current Configured Preferred Server is Not Available. Using 'PlugIn Server US (CBOE)'
Simply extract the plugin file from download section to your %appdata%\OptionsOracle folder (Create one if you don't have it already there) and run options oracle. Hurrah the error is gone and you will now be prompted to update plugins as well. You should also be able to see the list of plugins available in the configuration option. Enjoy!!!
NOTE: Please enter ^NIFTY as the symbol for Nifty. Lots of people are entering incorrect symbol which is why they don't see the data.