Jquery AJAX XMLHTTPRequest has no useful information in error state

I'm running into brick wall after brick wall. I have an application that is making an AJAX call, but seems to never hit the server. Instead, jQuery returns with an error status in the XMLHTTPRequest object. If my XMLHTTPRequest object returned is called xhr, here is the relevant information:

xhr.statusText == "error"
xhr.readyState == 0
xhr.status == 0
xhr.responseText == undefined

This has been working in the past, and this problem seems to have come on with no prompting. Also, I have trie开发者_StackOverflow中文版d in both IE and Firefox, and Firefox seems to work fine. The problem only exists in IE8, where I am using compatibility mode.

Does anyone have any idea what could be going on here? Any insight would be greatly appreciated. Thanks.

Using the GET method for my AJAX call, the problem was that the number of ID's being passed to the controller ran up against IE7's (stupid) limit of 2048 characters. So I changed the method to a POST, and that seems to have resolved the problem.

I should post a new question about what to do when you encounter a situation where you need to use a GET, but need to pass down an indefinite number of ID's to assist you in calculating the value(s) returned.