Before some days I have problem with my feed, basically feedburner not delivered any email to my subscribers & showing this message “Your Feed size is more than 512k limit, Please reduce this.” also webmaster is showing your feed is corrupt or bad. I found a great solution to resolve this problem. Check out following steps to Re-generate your Feedburner Feed.
Sign in to your FeedBurner account.
Click the title of your FeedBurner feed on the My Feeds page.
On the feed management page that appears, click the Edit Feed Details… link just below your feed’s title.
In the Original Feed Address field, change the address listed there from an example like the following: