When trying to add a new thread to a private forum the following error comes back. Setting the forum to public works without an issue: Tried private with and without post restrictions and no moderation both error-ed. Replying to the post works fine.

Error: is currently unavailable.
DotNetNuke.Services.Exceptions.ModuleLoadException: Value cannot be null. Parameter name: collection ---> System.ArgumentNullException: Value cannot be null. Parameter name: collection at System.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument) at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection) at DotNetNuke.Modules.Forum.PostEdit.cmdSubmit_Click(Object sender, EventArgs e) --- End of inner exception stack trace ---