Just you I guess. I have no problem using the up - down arrow keys, or Page Up and Page Down, in either the Bookmarks Sidebar or the Bookmarks Menu drop-down as long as focus is on those two areas.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do not click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

That didn't help. I found that if I press the cursor keys first, then the Home and End keys work, but the PageUP or PageDN keys don't work at all.

Does this work in the Bookmarks and History Manager (Library)?

• Bookmarks > Show All Bookmarks

You can check for problems with the localstore.rdf file.

• http://kb.mozillazine.org/Corrupt_localstore.rdf

Create a new profile as a test to check if your current profile is causing the problems.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer some files from an existing profile to the new profile, but be careful not to copy corrupted files.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

This is a brand new profile. I'm considering Firefox as a replacement for IE9, but so far it isn't working very well.