I tried creating a post with these four characters (without the space) and received a 404 error whenever I tried to preview or save:
I wrote a post about it here on my blog:
I've tried this on three different blogs, including a WP v2.3.3 installation. However, a friend of mine who is running WP v2.3.2 on a different server doesn't have this problem.
Separating even one character with a SPAN tags fixes the problem, but alone I cannot save the post.
Any ideas? Does anyone else have this problem?