Ok, I did some more testing and here is what I discovered.
The source snippit for the link I'm clicking on is here:
<ul>
<li id="deck_33452" class="submenu_entry deck "><a href="/sets/33452" title="RDW - Koth, Dragonlord" class="simple"><img src='/images/icon_spacer.gif' class='sprite s_deck ' title=''/>RDW - Koth, Drago ...</a></li><script>Tcg.folders.setupDeck(33452);</script><li id="deck_33449" class="submenu_entry deck "><a href="/sets/33449" title="Vampire" class="simple"><img src='/images/icon_spacer.gif' class='sprite s_deck ' title=''/>Vampire</a></li>
<script>Tcg.folders.setupDeck(33449);</script>
</ul>
The main issue seams to be that the <a> tag isn't getting activated. I think the <a> isn't getting activated because a parent control is draggable the begin drag operation is getting called first even though I am not actually dragging the object. I say this because of the observed behavior. When I click down it starts the drag operation. Likely this is eating the click event. While the double click event is getting through. I'm not familiar enough with the call stack here to help further.
I hope this helps you find the issue.
I also reproduced this issue in IE 8.0.