LabTutor requires the use of native XMLHTTP in Internet Explorer. If you experience a situation where after opening an experiment the forward and back buttons remain disabled, the Start and Home buttons are missing and the experiment status remains as 'Loading...' then it is possible that native XMLHTTP support has been disabled in Internet Explorer (either by the user, or by the administrator though Group Policy).
To see if this setting is disabled you can check the Enable native XMLHTTP support option in the Advanced setting tab of Internet Options dialog box in Internet Explorer (Tools -> Internet Options -> Advanced -> Enable native XMLHTTP support checkbox).
If this option is disabled you must enable it for LabTutor to function as expected. An example screenshot is located HERE
of what you might see in LabTutor if this option is disabled.