Not here. I think this has more to do with your system O/S then FF. FF more or less magnifies the problem because it can process FF request is more akin to the problem. So what O/V version and what FF version along with are are they both x64 or x86 verison?

I use windows 10 , 20% disk occupied on a fast laptop , the new version is much slower than the previous an clunky and slow on startup.

Go to the Firefox 3 Bar Menu --> Help ? --> Troubleshooting Information Page and take a look in the Accessibility section if accessibility is set to "true" there. if yes, go to the Firefox 3 Bar Menu --> Options --> Privacy & Security panel and under Permissions check the setting to Prevent Accessibility Services from accessing your browser. Restart Firefox Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there? If No then is a Extension or your Profile. https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-ram https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles Please let us know if this solved your issue or if need further assistance.