essentially IE was caching the results from my script even when offline meaning it always thought it was online, adding a timestamp to the url that xmlhttp.open was calling solved the problem.IE6 and IE7 use some agressive cache, that caches all the ajax. Essentially, if you update the inserted code, IE fails to use the new version, favouring the cache version every time.
Thought I'd post it in case anyone else winds up pulling hair out trying to understand why an ajax call seems to be doing nothing