As an altoholic and recipe hound, I have a lot of addons installed to make my life easier. CT-mod forms a great deal of my UI, Recount for my personal knowledge of how well I'm doing in groups, Omen threat meter to know when to back the fuck off on my DPS so the mob doesn't decide that I'm a tastier target than the tank.
However, Ackis Recipe List has recently made opening my profession books kinda....agonizing. With addons turned off, it's instant. With Ackis and ProfessionsBook turned on, it can take a few MINUTES to load my alchemy book when I'm trying to do my daily transmute.
I finally decided to find out what the problem was, and with a little googling, I determined that deleting my WTF and cache folders would probably be a good idea. I did it, and it made a world of difference.
So if you ever have a problem of lagging while checking your professions, try deleting the WTF and cache folders.
P.S. You might want to make a copy of the two folders on your desktop first, just in case.