I was using my computer a couple of days ago with no issues, shutdown the computer for the night, then the next day there is a delay for the context menu to show up after right clicking in both Firefox and Thunderbird. Aside from installing a few updates I have not made any changes to the computer since the day before & I have no issue with context menus in other browsers or the OS. The hardware a Dell Optiplex 790 with an i5-2400 quad core, 12 Gb ram running Ubuntu 17.04 64bit. The symptoms: - The right click context menu takes approx 5 to 8 sec to show up. - Drop down menus on web pages & in settings behave the same. - Occasionally the FF window will darken for a second or two then return to normal. - When an option on the context menu is clicked it is taking about 3 sec to go through. Fixes tried: - New Profile. - Safe Mode. - Disabling Hardware Acceleration. - Complete removal of FF & TB as well as their folders. - Downgrading to FF version 50. - Checked on another computer (this one is running Lubuntu, & does not show the issue). Does anyone have any ideas?