Hey there. I wouldn't know about Farmville specifically, but there was a performance regression fix in Firefox 45.0.1 that might help. Please visit https://www.mozilla.org/en-GB/firefox/new/ to update your browser and then stop by https://www.mozilla.org/en-US/plugincheck/ to make sure your plugins are up to date. If updating does not resolve the issue, try running Firefox in Safe Mode, https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode#w_how-to-start-firefox-in-safe-mode. This will disable Themes and Extensions and override some settings that may be causing problems. If Safe Mode works, we can try and find out which add-on or setting might be the culprit.