This started happening to me a week or so ago using version 2.6. I upgraded to 2.6.2 and it's still happening.
I'm using w.bloggar to post to WordPress using xmlrpc. Whenever I post, the less-than and greater-than characters get stripped out along with single and double quotes.
I've tried using Windows Live Writer and the exact same thing happens, so I don't believe it's the desktop programs, but something with the WP install.
Any assistance or insight would be much appreciated.