I am posting this in the off chance there is a SCORM expert out there that may have seen something similar.
Internet Explorer 8 gets "stuck" on step 14 of test case SX-05. Something doesn't trigger the continue. No amount of debugging and tracing reveals anything. It's as if the test case is "overwhelming" IE8's slow JavaScript engine. All other tests run fine in IE8. This one is quite complex, but there are others of similar complexity.
This turned out to be rather obscure. Our LMS was writing a loading page to the content iframe before loading the actual SCO.
window.frames.contentFrame.document.open();
window.frames.contentFrame.document.write(html);
window.frames.contentFrame.document.close();
I changed the loading page to a static HTML page and everything chugged along fine. Modifying the document that way screws up some window events on Firefox and IE.