OK, I think I've fixed this (error and no pop up navbar in IE) - but you may want to check this because I am no coder...
This mod is a form, but it's stuck in the middle of another form. If the mod is displayed, it just terminates the first form. This is how I fixed it:
Admin CP -> Styles & Templates -> Style manager --> [Style you want to edit] --> Edit templates --> Forum Display --> FORUMDISPLAY
Find and delete:
PHP Code:
<form action="inlinemod.php?forumid=$forumid" method="post" id="inlinemodform">
<input type="hidden" name="url" value="$url" />
<input type="hidden" name="s" value="$session[sessionhash]" />
<input type="hidden" name="forumid" value="$forumid" />
Find:
PHP Code:
<if condition="$pagenav">
Insert
above/before:
PHP Code:
<!-- START FILTER TEMPLATE EDIT -->
<if condition="$show['threadprefix']">
<td class="smallfont">
<form action="forumdisplay.php" method="get">
<input type="hidden" name="s" value="$session[sessionhash]" />
<input type="hidden" name="f" value="$forumid" />
<input type="hidden" name="page" value="$pagenumber" />
<input type="hidden" name="pp" value="$perpage" />
<input type="hidden" name="sort" value="lastpost" $sort[lastpost] />
<input type="hidden" name="order" value="desc" $order[desc] />
<input type="hidden" name="daysprune" value="-1" $daysprunesel[all] />
Show only the following: $threadprefixes
<input type="submit" class="button" value="Show" /></form></td></if>
<!-- END FILTER TEMPLATE EDIT -->
<!-- Form code moved from section Threads List -->
<form action="inlinemod.php?forumid=$forumid" method="post" id="inlinemodform">
<input type="hidden" name="url" value="$url" />
<input type="hidden" name="s" value="$session[sessionhash]" />
<input type="hidden" name="forumid" value="$forumid" />
<!-- End of Form code moved from section Threads List -->
This works for me on 3.6.5, it removes the error message in IE, and doesn't break inline moderation.