First, let's make sure it's not just a profile issue. Create a new Firefox profile and see if things are still slow without any additional add-ons. (
Win+R>firefox.exe -ProfileManager) If it's not, start removing add-ons and restarting until you find the culprit/culprits. (this should be a similar test to safemode, but sometimes profiles get all wonky and you just need a new one)
Okay, if that wasn't it, how about it being a local Firefox issue? Go grab a copy of PortableFirefox and see if it's slow in there.
If that works, check to make sure you are using tracemonkey in your local copy (though your examples shouldn't require the JIT).
about:config search for
jit make sure
Check to see if you've got some invasive script checking anti-virus making your life difficult (or several anti-virus/malware packages running at the same time). Disable any and all and try again. Is it also slow in IE (we know it's not in Chrome, how about Safari, Opera), because maybe the sandbox in Chrome is hiding it from something on your system.