I also have this problem though for me it is not permanent it works perfectly fine untill i hit the first site using flash installed then it does not, i installed firefox 4 from scratch it was not upgraded from a previus version.

actually reinstalling flash and firefox seams to have at least temporary solved the problem

Thanks for the reply. As far as I can tell, the websites I'm opening do not use Flash.

But how would I know for sure? For example, does this page use Flash? I don't see any animation so I think it doesn't, but I really don't know.

That said, Page Up and Page Down also don't work on any other pages I've opened. As this was driving me crazy, I uninstalled Firefox 4 and reinstalled 3.6.x. Call me eccentric, but I need to be able to page-down, page-up.

Minus this problem, I liked everything else about Firefox 4 and would love to re-migrate in the future.

If anyone knows of fix or work-around, please advise.

Thank you.

--Dan