One possible reason is that when you went back, that page navigated to a new page on its own, wiping out your previous forward history. If you right-click the Back button, do there seem to be an unexpected number of entries for that site?

By the way, your "More System Details" shows that there is a optional user.js settings file in your profile folder. Unless you created that file, other software may have created it for its own reasons. The settings in a user.js file will override your previous session settings at startup, so you might want to investigate or remove the file. This article describes how: How to fix preferences that won't save.

I should add that the History menu may still list those pages, as it lists 12-15 of the most recently loaded pages regardless of what tab loaded them. You can access that using either:

• "3-bar" menu button > History (look below the recently closed tabs and windows)
• (menu bar) History menu -- you can tap the Alt key to display the menu bar temporarily if you don't usually show it
• History Sidebar (Ctrl+h) -- this can be sorted in various different orders

Was hopiing for a way to restore the forward and backward arrows, but this will do. Everything that was intuitive in XP is now a major operation in 8.1.

Thanks for the help.