We got the same problem in our solution, same error message. It only applies to the DateEdits that has VistaDisplayMode = True. If we set this to false everything works fine, but some of our controls would need the optional EditTime that VistaMode enables.
I don't think it is something wrong with the skin, since we have tested without our custom skin:
First we deleted the references to our custom skin and used devexpress default skins (caramell, black and pink tested). Didn't help.
We also deleted the DefaultLookAndFeel from our mainform, this didn't resolve it either.
We had another bug with the DateEdit, it got a HUGE red X on white background when it popped up and fired an exception, this was fixed when we discarded our custom skin and used default devexpress skin.
-Anders