You id is David 470 (space in id), due to this space your id in rss feed is David+470, which not correct format according to Feedcat.net. No, need to feel sad.
copy ur rss link & paste in tinyurl (dot) com, make ur rss link tiny ( actually we want change this rss feed ), now copy ur tinyurl & insert in feedcat.net
Voila, they accepted :)
Definitely your problem solved by this process (but if you not understand this process due to my poor English so, PM me I will send screen shot of this process ).