If I change any in the forum setup I get te following critical error "The added or subtracted value results in an un-representable DateTime. Parameter name: value" and then the forum stops displaying and the only thing that it displays is "Viewable by Administrators Only" in the container.

I'm logged in as Admin when it is showing that message so it is not a permission issue with the page or module within dnn, it also shows that message at the top before I change any settings on a new forum module before the main portion of the forum module disappears.  I am working with ver 4.X of DNN.  Is it possible that this is a windows file system permission issue?  I recently made some changes to the system that wipped out a lot of my permissions and I had to restore most of them.  I had to add back in a lot of access for the Network Services user.  I thought I had pretty much everything working again, but maybe I don't.