Sidebar Nav Missing on Some Pages and Posts

Hi all. I’m using WP 3.3.1 with a modified Dynamix theme. I’m having this problem where on some pages and posts the left sidebar nav is missing. All pages are configured the same with in the admin to have 3 columns and sidebar1 on the left and sidebar2 on the right, yet new pages I add are not displaying the left sidebar.

Here’s a working page:
<a href="http://wpdev.onenetwork.com/supply-chain-management-solutions/intelligent-logistics/">http://wpdev.onenetwork.com/supply-chain-management-solutions/intelligent-logistics/</a>

And here’s a non-working page:
<a href="http://wpdev.onenetwork.com/supply-chain-management-solutions/parcel-management-solution/">http://wpdev.onenetwork.com/supply-chain-management-solutions/parcel-management-solution/</a>

Working page source code:

<div class="side-wrap left out-quarter">
<div class="border-wrap left in-full border bottom">
<div class="border-inner border">
<div class="sidebar-content out-full border top">
<ul>
<li id="multi-level-submenu" class="widget widget_subMenu"><ul class="menu subpages"><li class="page_item page-item-2067"><a href="http://wpdev.onenetwork.com/supply-chain-management-solutions/commercial-supply-chain-solutions/">COMMERCIAL SOLUTIONS</a></li>
... etc ...
<li class="page_item page-item-909"><a href="http://wpdev.onenetwork.com/supply-chain-management-solutions/handheld-devices/">Devices</a></li>
</ul></li>
</ul>
</div>
</div>
</div>
</div><!-- /side-wrap -->

The non-working page has the code for the sidebar but the UL is empty, no LI tags.

<div class="side-wrap left out-quarter">
<div class="border-wrap left in-full border bottom">
<div class="border-inner border">
<div class="sidebar-content out-full border top">
<ul>
</ul>
</div>
</div>
</div>
 </div><!-- /side-wrap -->

Any clues? Nothing on the code side has changed so reluctant to start digging through sidebar and functions files. I’m puzzled as to why this started happening, and why existing pagesposts are fine, but not new pages/posts with exactly the same layout configuration.