When building the site map manually for the first time, the script continually loops and can only be halted via the browser. The sitemap appears to be generated without any problem and subsequent manual rebuilds are problem free. It's just the first time that the looping occurs. I've now had this happen on 3 different WP installs. All 2.8 using XML Sitemap 3.1.3. The only common active plugins were Akismet and Quicktag Extender.