Can’t import rss in Invision Power Board after upgrade to wordpress 2.7

Invision can’t validate the rss feed.

if i try to update

RSS Import(s) Re-cached
Could not open http://www.madboxpc.com/category/noticias/rss to locate channels.

if i try to validate on ipb

Validation Results for http://www.madboxpc.com/feed
· HTTP Status Code: 301 (Moved Permanently)
· We could not determine the feed’s character set
· We could not find any channels in the RSS feed (nothing to import).