[jQuery] .load() doesn't work on first call in FF3 and IE (But works in FF3.5)?

[D A]

We're attempting to load a snippet of XHTML into a container on a page
via .load() from a fancyBox pop-up.

Here's the bit of jQuery we're using:

$('#LocatorGoLink').fancybox({
                        'hideOnContentClick': false,
                        frameWidth: 660,
                        frameHeight: 700,
                        overlayOpacity: .6,
                        padding: 0,
                        callbackOnShow:
function(){$('div#resultsDataContainer').load('locatorResults.cfm,{'zip':$('#branchLookup').val()});}
                });

We're getting some odd results cross-browser.

If we view our pages on our local file systems (windows) (the CFM page
just being a simple XHTML document) the results:

FF3.5 = it works
FF3 = nothing loads (and no .js errors)
IE6 = nothing loads (and no .js errors)

If we post them to our dev server and try again, we get these results:

FF3.5 = it works
FF3 = nothing loads the first time we trigger the event. It works on
every subsequent trigger.
IE6 = nothing loads the first time we trigger the event. It works on
every subsequent trigger.

Any ideas why? I'm hoping there's a common issue we're overlooking.
Google hasn't found a whole lot but I did come across this:

http://zacster.blogspot.com/2008/10/jquery-ie7-load-url-problem.html

Where there appears to be some browser caching issues (maybe that
explains our local issues?)

-DA