Well I noticed that everytime that a bubble text appears while questing, the wow client crashes. Also when running wow in 64 bits the game never freezes nor crashes. So it looks like the problem is clearly due to wow client running in 32 bit.
Btw if you look on the US and EU forums of wow you will see many people complaining about freezes and crashes when running wow in 32 bits.
I don't know if it's on purpose but it looks like botting is almost impossible right now.