Well after at least a year of struggling with this stupid router, I threw it against a wall. Very liberating and I encourage others to do it!

All the problems started when I upgraded to 1.21.
I tried everything from this forum. When I upgraded to 1.22a, I was hopeful at first, because it worked ok for about a month, but then suddenly the same problems, inexplicable wireless dropouts, inexplicable LAN dropouts.
Then I tried to downgrade back to 1.15. No luck, same issues.
So I bought the apple airport router. Zero issues, flawless performance.
Then I threw the 4500 against a wall. Will never buy D-link again.
Sorry, just wanted to rant for all the hours of my life I want back.