My Help was working fine a month ago - hadn't used it since then.
Tried it last night on the mail app (wanted to know how to write a rule/filter) and it behaved the way that you mention.
I have updated to the newest developer release of Java 1.4.2 and it broke a bunch of my apps and so I figured it was related to that. But if you haven't done that, then perhaps it is something different.