My bad. It's not a bug afterall, just poor coding on my part. Or probably because IE sucks anyway ;)

I replaced this

<a href="javascript:OpenLatexEditor('whatever-id-name-you-want','phpBB','')"><input type="button" class="btnbbcode"
name="Equation Editor" value="Equation Editor" /></a>

with this

<input type="button" class="btnbbcode" onclick="javascript:OpenLatexEditor('kambing','phpBB','')" value="Equation Editor"/>

And now it all works fine in IE.

That sample code would be useful. But I think it'll be very laborious for you to provide workaround for every major editors. Maybe you can focus on popular choices like joomla, vbulletin, wordpress etc.

Cheers