I've not tested this purported "work-around"--but if it won't create a TOC, then it's not a workaround. The whole IE9 compatability issue was predicated upon, and caused by, the creation of a TOC, which was when MBPC would crash if Exploder 9 was installed on the same computer. If DDHarriman's observation is correct, then this "workaround" solves absolutely nothing, and MBPC is in the same state it was prior to the "fix." The post IExploder9 problem was that MBPC would crash when asked to create the TOC, so...not sure I understand what this solution fixes, as it worked fine post-Exploder9 as long as one wasn't creating the TOC therein?
I frequently recommend MBPC to noobs trying to learn now to make basic (k7) Kindle books, if they don't have Exploder9 installed, and had hoped that this "workaround" would allow me to do so again, as most noobs aren't quite up to using something like Sigil yet--but it doesn't sound like the workaround worked--if it crashes during TOC creation, then, what, exactly, is it purported to "fix," since the TOC creation was the only thing that was crashing in the first place?