Hi Lee,
I didn't debug the page - so don't know the exact cause. I did notice that when you logged in on any page that had a QRB, instead of tabbing to the password field you tabbed directly into the QRB. I tried messing around with "tabindex" but gave up because I couldn't get rid of the error warning in the status bar - and because I hit on a better solution.
Now whenever a guest views a thread they see the reply button. When a member views the thread they see the QRB. It just means one extra click for guests - but I'm quite happy to point out the fact that they will have 'in line' reply facility as soon as they register
Thanks for your help though.