You might try submitting your url for each of your pages to one or more of these siteshttps://browserlab.adobe.com/en-us/index.html#http://browsershots.org/
This can be very very slow so suggest trying one of the free trials first.http://crossbrowsertesting.com/
Use free trial. The free trial here works very fast
For a good quick check against various flavors of IE go to http://ipinfo.info/netrenderer/
Probably this is the best place for you to start. I checked your East Coast Tasmania page here and found it did not work with IE6 but seemed fine with IE7 to IE 9.
You can check your site's compatibility with all the common and most uncommon browsers.
This should show you where you might have a problem.
As I said before, your site works fine on my desktop Windows7 64 with IE8 and Firefox 4. It also works fine on my laptop with XP Pro and IE8 and my wife's computer with XP Home and IE8.
Is it possible that your work computer is using an older version of IE? Or maybe one that was modified somehow?
Also suggest you check your site with the one of the html/CSS validation programs offered here http://www.thefreecountry.com/webmaster/htmlvalidators.shtml
You might also want to look at the error console in Firefox (under web developer menu on Firefox 4) and see if it reports an error.
Sometimes something simple, like not closing an html tag, can cause problems with one browser and not another.
I doubt that this is the problem, but the validation is quick and free.