The current version of Greasemonkey is compatible with Firefox 29. Could you check to make sure it is not turned off? There should be a "monkey" icon on the toolbar. Clicking that icon turns Greasemonkey on and off; the "off" state is designated by a faded icon, while the "on" state has a full-colored icon. ---- More generally, could you check for possible extension updates and disable unimportant extensions in case one of those conflicts with Firefox? Open the Add-ons page using either: * Ctrl+Shift+a * "3-bar" menu button (or Tools menu) > Add-ons In the left column, click Extensions. Then, look for the "gear" button above the list and choose Check for Updates. I also suggest disabling any extensions you won't be using for the next 24 hours so that you can test whether that improves Firefox's functioning. Usually a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step. Any difference? ---- One possible reason for hangs, especially where you eventually get a dialog indicating that a script is running slowly, is Flash. To minimize sites from using Flash unnecessarily, try setting Flash to Click-to-Play ("Ask to Activate"). This will delay Flash from starting on a page until you approve it. On the Add-ons page, in the left column, click Plugins. Look for "Shockwave Flash" and change "Always Activate" to "Ask to Activate". When you visit a site that wants to use the Flash, you should see a notification icon in the address bar and one of the following: a link in a black rectangle in the page or an infobar sliding down between the toolbar area and the page. Any noticeable difference?