Main site RSS won't validate

I am perplexed. My main websites RSS feed (www.geekazine.com/feed) will show up in a browser in under a second. When I go to validate it at W3C (and other validators), it times out. If I validate any other RSS feed in my multisite (www.ipad-365.com/feed) it says the feed is valid.

So far I
– refreshed my plugins
– turned off and deleted all cache information
– changed my RSS number to 1
– repaired and optimized all tables
– changed the theme to WP2013

No change.

What could be causing this?