Recently I upgraded my WordPress plugins to jQuery version 1.7.1 and noticed that Internet Explorer 8 was causing errors “‘null’ is null or not an object”. I isolated this to the SyntaxHighlighter Evolved WordPress plugin I was also uses.
On further Googling it seemed that there were issues with the XRegExp library and jQuery 1.7.1, reported by other uses on IE 6 to 9. Schabse Laks posted a fix to the problem on his blog, though this gave me a new error, so I have modified it slightly, modification on line 271;
RegExp.prototype.exec = function (str) {
if (typeof(str) !== "string")
str = String(str);
var match = real.exec.apply(this, arguments),
name, r2;
Download the resolved SyntaxHighlighter files here
shCore.max.js
shCore.js