My Mac is a 21.5 in running OS X 10.9.3 and it has got really slow, and sometimes whey I am in Mail, I cannot select items, or when I hit trash nothing happens and I have to close out of Mail and start it again for it to work again. I emptied the caches to no avail. I just read a thread where TattooedMac showed how to reset permissions. Should I try this? Or should I get one of the Mac cleaners?