This may be due to a caching issue in Joomla 1.7. There are 2 ways to determine whether or not this error is related to Joomla 1.7's caching issue:

Method #1
Go to "Site > Global Configuration > System > Debug Settings" and set "Debug System" to "Yes". Visit the url of your RSS feeds and see if you can now see your RSS feeds. If you can now see the RSS feeds, then it is related to Joomla 1.7's caching issue. (Remember to turn set "Debug System" back to "No")

Method #2
If you have PHP error reporting enabled, you should be able to see the following error messages:
Fatal error: Call to undefined method JDocumentFeed::getHeadData() in /public_html/libraries/joomla/cache/cache.php on line 530
If this is the error message, then it is related to Joomla 1.7's caching issue.

Solution #1 (Temporary)
You can clear your Joomla! cache by going to "Site > Maintenance > Clear Cache", and you should be able to see your RSS feeds.

Solution #2 (Permanent)
For a permanent solution, you will need to modify "libraries/joomla/cache/cache.php" at around line 528.

Replace this line:
if ($loptions['nohead'] != 1) {
With this line:
if ($loptions['nohead'] != 1 && method_exists($document, 'getHeadData')) {

And you should be able to see your RSS feeds now.

Credits to Roy for provided the workaround at http://forum.joomla.org/viewtopic.php?p=2663979.