Deferred's resolveWith method fails on IE8 (with and without IE7 compat mode) when called without its second argument ("args"), e.g.,

d = $.Deferred();
...
d.resolveWith(this);

According to the docs, this arguments is optional, so this would be a valid call, and it indeed works as expected on at least Firefox and Chrome. IE, on the other hand, fails with an "Object expected" error.

A very small test case for the problem is available at http://jsfiddle.net/martinsoto/BLDTG/. It affects both jQuery 1.5 and 1.5.1.

I could trace this to the apply call at line 862 of jquery-1.5.1.js:

callbacks.shift().apply( context, args );

When resolveWith is called without the args argument, apply gets called here with an undefined but explicit second argument. This evidently makes IE choke.