A new bugfix release of Prototype have just been announced fixing crashes with versions 1.3 and 2.0.x of the Safari browser. It is highly recommended to upgrade to Prototype 184.108.40.206.
Excerpt from the prototype blog —”Previous versions of Prototype could trigger bugs in Safari's regular expression engine when updating elements with HTML containing <script> tags or when using JSON functionality with built-in security checks. These regular expression engine bugs affect Safari versions 1.3 through 2.0.4, but not Safari 3 beta or the WebKit nightlies. We've managed to code around them to prevent either browser crashing while maintaining the full API, keeping the performance top-notch and assuring backwards-compatibility.”