About how long before the trouble starts? [https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode Start Firefox in Safe Mode] {web link} A small dialog should appear. Click '''Start In Safe Mode''' (not Refresh). Is the problem still there? 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/firefox-takes-long-time-start-up https://support.mozilla.org/en-US/kb/quick-fixes-if-your-firefox-slows-down MemTest LAST UPDATED : 27/09/2013<br> Could you please run a tool from http://memtest.org/ in order to check the integrity of your RAM? You will need a thumb or disk drive to install it on. Do you let Windows handle the page file or did you set a fixed size ? If you use a fixed size for the page file then try the former and let Windows handle the page file.

but it's slowing down after a while like 1 hour. it's responding, not crashing, but pages opens veeery slowly. i tried ALL Firefox Tweaks... cpu,disk,ram - normal usage.

You can check the Firefox Task Manager (about:performance) and about:memory pages. *https://support.mozilla.org/en-US/kb/task-manager-tabs-or-extensions-are-slowing-firefox *https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-or-cpu-resources