Unfortunately, the Recall Monkey addon appears to be a Mozilla Labs project that has been abandoned. As Firefox advances, certain addons need to be modified by the addon developer in order to remain compatible with the latest Firefox. Clearly a change in the new Firefox has prevented Recall Monkey from functioning properly. Since it would appear that no one is maintaining the addon, there will most likely not be a new version released to patch this issue. If you are interested, you can search your history by pressing '''Ctrl''' + '''H''' to toggle the history sidebar. Alternatively, you can also browse through [https://addons.mozilla.org Firefox's many available addons] for an addon to replace the Recall Monkey. Sorry for any inconvenience.