Some feeds not loading and stuck in "!" mode.

I’m having trouble getting newsblur to find/load feeds. Here are some examples:

I’ve tried all three options in the “!” popup, and everything just hangs there. I also tried adding a new feed, and using either the site’s url or, when I found it, the rss url directly.

I had some other misbehaving sites, and was able to get them working by going to another browser, but these sites (and a few more) aren’t cooperating.