CONSTANTLY getting this very specific message: "A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can continue to see if the script will complete. Script: chrome://ytoolbar/content/utils.js:60"

'ytoolbar'is the Yahoo! Toolbar. You could try to update it. I will give you a fair warning that I see people struggling to change their search engine settings back from Yahoo, the Toolbar could be a culprit in that.

Or you can disable it. See https://support.mozilla.com/en-US/kb/Using+extensions+with+Firefox#How_to_disable_or_uninstall_extensions

I had the same problem. I uninstalled yahoo toolbar and reinstalled again and problem was gone

this is the error message that I'm constantly getting for the start of firefox

A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can continue to see if the script will complete.

Script: file:///C:/Program%20Files%20(x86)/Mozilla%20Firefox/components/nsBlocklistService.js:648

I have the same problem and believe the nsBlocklistService.js:648 refers to the Norton /Symantic security protection which is used to block phishing sites. I use Norton 360 and suspect it is the cause. Are you also using Norton?