Hi, I found this seems to relate to jQuery bug 6314 (http://dev.jquery.com/ticket/6314). In IE7, if "Enable native XMLHTTP support" is checked (under Tools > Internet Options > Advanced tab > inside the security section) then this error shows up. Unchecking/disabiling the option seems to resolve the error.

However, since I cannot tell all website viewers to uncheck that option, then the following code also seems to resolve the issue:
In non-minified jQuery, find the lines:
try {
var oldAbort = xhr.abort;
xhr.abort = function() {
if ( xhr) {
oldAbort.call( xhr );
}

onreadystatechange( "abort" );
};
} catch(e) { }

replace it with the following code:
try {
var oldAbort = xhr.abort;
xhr.abort = function() {
if ( xhr) {
if (oldAbort.call === undefined) {
oldAbort();
} else {
oldAbort.call( xhr );
}
}

onreadystatechange( "abort" );
};
} catch(e) { }

I believe the issue is as stated by other users in this forum, that the xhr (XMLHTTP) object is a native IE object, so the abort function on the xhr.abort function does not support call.