Thanks for all the valuable input, folks. I will take a step back and relook all my pictures again.
Here are 2 of the photos that were cited as 'Noisy'
http://www.flickr.com/photos/60733744@N00/2954734542/in/set-72157608176696161/
The area which I could really see noticeable noise would be the 2nd column of windows from the left? But then, thats my amateur yardstick.