Well, rather than deleting this post...  I'll leave it here for the benefit of the community.

The Web.config explains this in very good detail --- nice, Joe!

<!--
Disabling viewstate at the page level can reduce the size of the page
which improves performance. Modules that do postback usually need
ViewState Enabled so in the Page_Load event of modules that postback
I add a line of code like this
Page.EnableViewState = true;
This works fine for all the built in modules but I've had at least one
developer tell me it did not work for his custom modules so I added this
setting here which you can set to false if you find it breaks any functionality
in your custom modules. If it doesn't break anything I recommend leaving this
set to true
-->
<add key="DisablePageViewStateByDefault" value="false" />

Setting the view state in the module does the trick!