Recent Global Comments feed Validation

I have installed the recent-global-comments-feed and edited my .htaccess accordingly. I installed comment-indexer and ran the sql queries successfully.

Yet validation of this feed fails:
http://rvblogz.com/global-comments-feed/

FeedValidator reports:
Sorry
This feed does not validate.
line 13, column 10: pubDate must be an RFC-822 date-time:
<pubDate></pubDate>

Does it usually take time or comment traffic for the feed to populate?