I seem to be having a conversation with myself, but I hope it will help someone in the future.
So, just disabling SEP did not seem to work, so I decided to completely uninstall it. Problem fixed.
I guess I'll have to look into another virus program as it will be cheaper than changing out the router, but this seems to be a pretty known and documented problem - shame on DLINK for not putting a sticky on it or making an announcement or FAQ.