afxGlobalUtils.GetDockingManager(pParentFrame); returns NULL

Question

Having odd bug in my mfc single doc program (VS2008). When calling AFXPrintPreview(this), an assertion gets tripped. Looks like on line 181 of afxpreviewviewex.cpp, when mfc tries to get a hold of the docking manager, it just gets NULL, which trips an assert when mfc attempts to add a pane on line 183. Specifically, I get the print statement: ASSERT_VALID fails with NULL pointer. The parent frame being passed into GetDockingManager() is definitely my main frame. I would assume this means that there's some initialization my frame must be missing?