Sorry to bring a thread back from the dead, but I’ve been experiencing this trouble, too. My host and I have been working on this for two days so far, but we haven’t been able to solve it, except to strip most–if not all–of the HTML tags… which iampetesmith said, isn’t a viable solution for a blog.
Here’s a stupid question: could WordPress one day be able to work around this, or is this entirely a server thing?