ArgumentException when selecting Hacker News items

[hannesschulze]

Sometimes, after switching between different Hacker News items, an unhandled ArgumentException is thrown with the following message:

Source object type is not a projected type and does not inherit from a projected type. (Parameter 'value')

It seems like the comments are loading fine (breakpoint at the end of FeedViewModel.LoadItemContent is reached) and the comments view model also seems to have loaded (breakpoint at the end of CommentItemViewModel.Load is also reached). Unfortunately, I don't know any way to debug an UnhandledException properly.