The history is usually very large for most users so it makes sense that it would take a long time for it to show up. This might not help for this specific case, but try clearing your history. It will probably make loading faster.
You can clear your history and other private data by going to Tools -> Clear Private Data or by pressing Ctrl+Shift+Del. You are then given the option to clear your history and several other things such as saved passwords and cookies. Note that when clearing your private data it may also take a very long time and Firefox might freeze up. Just be patient and let it work. If it's taking more than 15 minutes to clear, then close Firefox and try again.
