This post in the Apple Forums solved the problem for me
http://discussions.apple.com/message...187323#1187323
There's more in that thread I've not read yet but start there.
The only folder I've ever made read only (after deletion and recreation) is
/Users/xxxxx/Library/Caches/com.apple.helpui/Mac Help
and it's been working for quite a while. I'm running 10.4.5 and no updates have solved the problem yet.