Hey guys, I and many others have been having issues where as soon as you entered combat your framerate would drop to 1 or 2. Now this fix is only for those of you that use X-Perl Unit frames.
As you know pet happiness was removed from the game with 4.1, however X-Perl still refers to it in its lua script so I am going to show you how to edit those lines of code out.

First go to your WOW/Interface/Addons/Xperl_PlayerPet folder.

Then open XPerl_Player_Pet.lua Windows may not recognize this file type so open it with notepad.

- hit ctrl+f to open a search box and paste local happiness, damagePercentage = GetPetHappiness() into the field then hit enter.

- delete damagePercentage = GetPetHappiness() and replace it with damagePercentage = 3, 125

- hit ctrl + f again and paste UNIT_HAPPINESS from XPerl_UnitEvents registration into the field, hit enter.

- The line hightlighted should look like "UNIT_PET_EXPERIENCE", "UNIT_HAPPINESS", "UNIT_POWER"})

- remove UNIT_HAPPINESS, make sure to remove the quotation marks and extra comma.

- The Line should now read "UNIT_PET_EXPERIENCE", "UNIT_POWER"})

I hope this helps some of you.