Twitter Card not working

Hi – I have been trying to get twitter cards working with no luck. I keep getting a server error when I try to validate the following link http://sparkline.motifinvesting.com/housing-recovery-soon/3033 at
https://dev.twitter.com/docs/cards/validation/validator

When I try to manual insert the image into the validator I get – Failed to get a proxied URL for the image.

1. My robots.txt is allowing the twitterbot
2. I have a featured image set.

Have others gotten this to work?
Do you see what I am doing incorrectly?

Thanks!

http://ww.wp.xz.cn/plugins/seo-ultimate/