Oh, right. I remember now that I've had exactly the same problem once, only with html from database and/or generated by Xinha/FCK Editor. However, I didn't find any solution, but I believe it has something to do with some php.ini setting, or perhaps even apache's gzip handler. This used to happen on some versions of php 4, not on 5. So, it might aswell be a problem of the build you're using, although I might be wrong about this.
I have optimistic thoughts, even though sometimes (if not always) life's a bitch.