Sanju-
I don't have an answer for your question but I've had my own ups and downs with DNN Search for several years and eventually switched to using free Google AJAX Search for many of the sites I create.  If you cannot get a resolution to your issue with DNN Search you might consider trying out Google AJAX Search for your site (see link, below).

Google AJAX Search for DNN
Here's a step-by-step article on how to modify a DNN skin to replace DNN Search with Google AJAX Search.  The article includes a working example of the AJAX search:

   http://googleAJAXsearch.com
 
Here are a few notable features/advantages of the Google AJAX-based search:

• Search results are returned on the user's current page instead of redirecting users to a "search results" page.
• Search is performed automatically as users type search terms without need for clicking a button or performing page postbacks.
• Search is perfomed "out-of-band" and asynchronously so searching does not interfere with playback of embedded music (midi, wav, etc), embedded video (YouTube, etc), etc.
• Users can click through multiple pages of search results without leaving or refreshing the parent page.
• You can code the search to perform multiple searches at once (example: use a single search to return results for matching web pages and return separate results for matching files).
• You can configure the search to only include results from one or more specific websites (they do not have to be your sites).
• You can configure the search to tie into a Google Custom Search (free) so that search terms and frequencies are tracked by Google Analytics (also free).

NOTE: CONTENT INDEX LAG
The main downside to using Google AJAX Search is that you have to wait for Google to index newly-added website content before it will show up in any search results.  By contrast, DNN Search is able to include new site content in its results as soon as new content is added (as long as the modules you're using directly support DNN search).  In practice I find that Google AJAX Search typically requires between 1 to 3 days for new site content to be included in search results.


Again - the linked article includes a working example of the Google AJAX search where you can experience many of the features I listed above.
 

Good luck!
-mamlin