I resolved my issue. Check out either the above issue or my comment to my blog post
I have tracked this problem down to something related to mod_cache and mod_rewrite conflicting on category rewrite cache keys. While I track down that issue I have temporarily disabled caching on my server which is a (low performance at least) workaround.
I am having a similar issue but i have no idea what is breaking it.
my support ticket is at: http://ww.wp.xz.cn/support/topic/129238
Peter
