FYI- I updated the support case with my new findings but I'll update this thread as well.

The Microsoft control set called ShapeContainer is what I believe is the culprit. It's some sort of container that covers the entire container behind the scenes when you add a shape control to your form. It looks like Microsoft wanted to make this container as invisible as possible, so you never see it until you look at the document outline or the source, and when you add or move a control on to the ShapeContainer it automatically gets sent to whatever control is the container of the ShapeContainer. I believe this is what is clashing with the shared controls. This is just a guess, but the WinTabControl probably has some code where if a shared control is moved or modified on any tab other than the shared tab, the control is temporarily modified on the non-shared tab and then sent to the shared tab afterwards. However the shapecontainer probably intercepts the control before the Infragistics code can do anything and sends it to the non-shared tab. In your tab, add some component from the System.Drawing component (I have LineShapes). This will create a shapecontainer on the tab. Now, add any control to the shared controls page. After that, go to the tab that you added the System.Drawing component and try to manipulate the control you added in shared controls. You'll notice that the control does not act the same way that it does without the shapecontainer. Primarily, the small box to move the control is not shown. When I resized this control, the control disappeared from the shared control page and became native to that tab.