OK, that is bizarre, considering I don't see it anywhere else in my application, but at least you pointed something to look at.
The issue is that I take Date/Time from a database and cast all the rows as DateTime objects. So when I see a generic error like this, it makes me nervous as hell because I have no idea where to start because I am not doing anything special on the web server.
Poking around for DT comparisons, that I can do. I certainly hope it is not in something that I did not write. :)