That little tiny detail about the Auto DNS, THAT was the problem, and there's a good chance this is a bug:
-I'm on 1.03.6h, that's the firmware that came with my router.
-I copied all the original config info into the VPN tab.
-I added my account number as the user/pass like you suggested.
-Then I tested it and sure enough it failed, tons of opendns "content blocked" errors for a guy who's never used OpenDNS in his life and never got these messages through their client - very strange.
-Just on a hunch, I said "lets see what happens if I turn off that thing you suggested to look at, and disable automatic DNS, then turn it back on again"
-After turning Auto DNS in the LAN tab off then on again, the VPN now works just fine.
The thing about all that is I never adjusted the Auto DNS settings before - All of this stuff that I'd been testing, trying to get the VPN to work were all off factory resets, cause at the time I thought that was the only way to fix this. And nothing about these VPNs told me I needed to change any DNS settings so I left it alone, Auto DNS never had anything in it it was never changed. Yet adding the VPN data, enabling it, hitting apply and going into the LAN tab, turning off Auto DNS then turning it back on somehow managed to fix the issue. Just on pure instinct, I looked at your suggestion and said "you know what, I never touched that setting before, there should be nothing in it, it should be clean... but I know my luck so you know what, lets reset it anyway" and sure enough, THAT was what fixed it.
Now I know you guys are working on a new firmware/OS, and if this is a bug that nobody knew about then I'd hate to see it end up in the new firmware too. Is there anything I can do to help you fix this?