Hello,
we have improved security in SP1 (mainly for people with self defense turned off) and it has impact on performance specially for users with lot of passwords, unfortunately the drop of performance is not linear and it was not spotted before release when we were testing the update.
We are working on fix and we will release emergency update as soon as possible. Also we have updated our testing procedures to prevent such issues in the future.
We are very sorry for troubles we have caused to our users, it was in good faith of making our secure product even more safe.