I have also encountered this issue within an FAQ section within a jQuery UI Accordion which has a similar structure to the following...
<fieldset class='inactive' style='display:none'>
I also have the following jQuery script powering it...
My experience has been as follows.
1) Developed the web app, which was being imported into a corporate themed webpage via an iFrame for showing management the intended end result. No problem.
2) Moved the web application code into the body of the corporate themed webpage (removed the iFrame). The problem appeared.
The issue is only present in IE8, and does not appear when I tested with compatibility mode turned on. Furthermore, the issue always reverts the numbering of the <ol> to zero. However, I can manually click on the number and it will then display the correct number. I hope this helps.