Our subscribers had problem from last few days regarding our feeds. As I was busy I couldn’t dig into more details then. The problem turn out to be some large posts made content larger than 512 KB, which is limit imposed by feedburner, the service I am using for burning my feeds. Below is screenshot of error page.
I should have taken issue more seriously but something like size problem was never crossed my mind. So sorry for inconvenience. Feed is now appearing in feed-readers as well as in inbox for those who use email subscription.