Firefox tab to fields and drop down lists with Mac OS X 10.5 (Leopard)

Has any one else noticed some problems after upgrading to OS X 10.5? It seems I can't tab to every field, such as the "Keep me signed in for today" checkbox on ebay's login page. I used to tab to it before upgrading. I'm also tabbing past some drop down lists where you select the state where you live in sign up pages. And before you suggest it, I have already turned on "All Controls" in System Preferences->Keyboard & Mouse. I don't think that affects Firefox anyway since it is a system controls option and doesn't affect the actions in a browser window.

Also, some drop down lists no longer drop down. I can focus on the list and even change the value using the up and down arrows, but the full list is no longer displayed. Again, this changed with the upgrade to Leopard.

If any one has experienced these specific issues or something similar please share your thoughts and solutions.

Mark