I have been having the following problem, i think it\'s probably due to the fact that my approach may be misguided, but hopefully with your help i can sort this out!
You'll have to use JSONP to do cross domain as far as I know - it's a security exception in AJAX. JQuery handles it nicely but, you will have to have the server reply modified to match it.
I have done an OSS project for Social Actions that does this using a PHP proxy. You can look at it here: http://os.adamaltemus.com/social-actions/