I might be the last person to know about this but I thought I would blog it anyways.
I wrote a post about Flex 360 - yesterday and copy/pasted some of the speaker information from another blog. Oddly enough, when I viewed the post, there were little squares in place of some of the characters. Since I had work to do, I dismissed it as an oddity.
An hour later, when my post hadn't shown on MXNA yet, I looked into it further. Apparently, the little squares caused the RSS format to be invalid and MXNA didn't pick up my posting. Even after I manually pinged it!.
I now dub the squares "The Square Of Death". All Hail Valid RSS