javascript - What could be stopping AJAX from returning? -

i'm trying troubleshoot problem on client's machine our website. we're using ajax call information on page select additional parameters. our callback function has block of code reading when ajax coming error or correct. every other computer we've tested with, ajax comes back. however, particular client, we're seeing ajax come error message, meaning response never got there or it's corrupted or broken.

does know how happen? client using ie 8 , i've tested ie 8, ie 9, ie 10, , chrome , of work on computers.

edit: of now, don't have access system , network causing error. trying see if can accept our domain , see if fixes it, right now, can't put fiddler on computer.

i've seen amount of random behaviour caused virus scanners , so-called network security products. try adding exception site security software client running.

the other thing use wireshark, fiddler, etc. see what's happening @ network level.