I wrote an extensive article about various root causes of feed RSS errors in WordPress and how to solve the problem.
Among many causes that I have experienced frequently is a bad post.
A bad post is not a bad writing or low quality article / post.
Google explains that a post is considered bad and will cause feed error if:
Your feed has these XML tags in it:
It is very likely that your feed will be considered invalid by FeedBurner, Feed Validator, and possibly many other places to which you want your feed properly distributed. The result is that FeedBurner will stop updating its version of your feed until the validation problem is repaired.
2. The Cause:
<o:p> tag is usually introduced by a copy-paste of original text from Microsoft Word or another Office application; this tag originates in a Microsoft XML “namespace,” or definition of a custom set of tags used for XML markup.
In general, using word processing applications to compose blog posts can lead to unexpected results (such as this one).
3. The Solution:
1. The best way to avoid this problem is to avoid composing and copying content from Word into your blogging tools.
2. If you still want to use content found in Office applications, a common trick for removing extraneous code is to “clean” copied text by pasting it into a plain text editor, such as Notepad (Windows) or TextEdit (Mac) and the copying the newly cleaned text before pasting it into your blogging application.
3. Compose new posts in a text editor recommended or provided by your blog platform publisher only.
The consequences of a feed error caused by bad post or others are many. Among which being (a) your post or articles will not be distributed, (2) if you integrate your feed with Feedburner and join Adsense for Feed, the Adsense will not show up in the feed. Thus missing potential revenue.
- Check regularly your feed’s health through feedvalidator.org
- If you join Feedburner, check also your Feedburner feed.
6. Feedburner Error and Solution
If you integrate your blog feed into Feedburner, you may look into the following issues and how to fix them 
The most common problems that affect your FeedBurner feed are:
1. The trouble: Your FeedBurner feed isn’t up-to-date with your Original Feed.
The fix: Try pinging FeedBurner using our Ping page. This action tells FeedBurner to go check your feed for updates immediately.
The fix: Check your feeds for validity problems: Original Feed Validity, FeedBurner Feed Validity. See if any errors are reported, Then, check out this help topic for removing unwanted characters from your posts if mysterious characters seem to be to blame.
3. The trouble: Connection timeouts between FeedBurner and the web server that hosts your original feed. If FeedBurner can’t reach your Original Feed for any reason, we will report it as a FeedMedic item here on Troubleshootize.
The fix: Try a ping once your website service has been restored.
4. The trouble: For podcasters, the web server hosting your audio does not report the correct content MIME type for your podcast files; FeedBurner doesn’t create podcast enclosures for these files.
The fix: Make sure your web server is configured to return “audio/mpeg” as a MIME type for your audio files (or whatever the appropriate type for your podcast media may be). This confirmation may require some help from your hosting provider if you do not manage your own web server.
5. The trouble: Your Original Feed is too doggone big! FeedBurner does not process feeds that are larger than 512K. Remember, your feed is an update on your content — not an archive for it — and you should use your publishing tools’ controls to make sure your feed doesn’t grow like kudzu possessed.
Resync takes the following actions:
1. Clears our cached version and refreshes its content from your Original Feed
2. Creates podcast enclosures for items that did not previously have them and contain links to podcast content
3. Reports any feed formatting problems encountered during the resync
When to use Resync:
1. As a last resort with a regular feed or a podcast, you can resync your feed.
2. You should only resync if (a) your feed is more than 1 hour out-of-date and (b) pinging FeedBurner does not update it or (c) your podcast files are not being turned into enclosures by our SmartCast service.
How to Resync Feedburner
1. Login to your Feedburner account
2. Click your Blog feed in trouble
3. Click Trobleshootize
4. Click Resync at the bottom. Done.
 Google Support
 Feedburner troubleshooting