How to solve "too much recursion" problem in prototype.js

In prototype 1.6.1_r2, the line numbers are:

Line 3890: expression.scan(/(([\w#:.~>+()\s-]+|\*|\[.*?\])+)\s*(,|$)/, function(m) {

Line 463:  this.gsub(pattern, iterator);

Line 423: if (Object.isFunction(replacement)) return replacement;

Replacing Event.observe(window,'load',function() {...}) with document.observe('dom:loaded',function() {})  doesn't help.