It has not "just about screwed everything up", every major update has it's problems. Maybe you don't remember v12 and back when all those new features were being added?
This may be because of your computer.Especially if you have an Intel video card.
it's because of the new download manger thing because it has to round up all of your activated add-ons you would only notice this if you have a stuffload of add-ons
This is the same thing that happens to me, although I didn't wait about 2 minutes. All I did was just turn off my computer and turn it back on. Basically, V18 has just about screwed everything up.