A month or so ago, an automatic Firefox update made my browser tedious in the extreme. Pages took an eternity to load. I scoured the Internet for advice on what was causing the slowness, ran Malwarebites to see if something was hijacking it, did every bit of computer maintenance possible, but without success. Then today as I went to clear the cache, I noticed a message that another update was ready to be installed and took a chance it wasn't going to make things even slower. It turns out it fixed whatever had been sodded up by the previous update and I'm back to normal again. If anyone else has been experiencing this issue, install the latest update to cure it.