What did you do and what did it do?
Did you zap the PRAM? Did you run it with minimum extensions? What happened? Did it crash? Did the Presto extension load or have an X through it? Where was the Presto extension loading? At the start or at the end? You can force the extension to load either at the end or at the start by using spaces before it or a ~ before it.
What's the deal with the RAM?