When attempting to browse your
Mark All Read page, it comes up completely blank; which wouldn't have been an issue with the patched or unpatched markallread bug you're mentioning. The bug was that users in IE couldn't mark their posts as read, but the page still loaded.
The updated file in the main install archive after Feb 23rd (or p2) should work; all that was added was adding a missing
Firefox and Chrome didn't care about this behavior change, but was added for IE users who where having problems.