1. Turn off Extensions.
Safari > Preferences > Extensions
2. Empty Caches.
Safari > Preference > Advanced
Checkmark the box for "Show Develop menu in menu bar".
Develop menu will appear in the Safari menu bar.
Click Develop and select "Empty Caches" from the dropdown.
3. Reset Safari.
Click Safari in the menu bar.
From the drop down select "Reset Safari".
Uncheck the boxes next to all items.
Check the box next to "Remove all website data".
I have exactly the same problem on mynew IMac, where Safari is running so slowly that it isnt reall running at all (plus my EnglishKeybard has seemingly reverted to a US Keyboard)
I folowed the above guidance to see whether it worked on the Imac as well, but it has had no effect whaseover.
IE workes perfectly OK on Parallels