A quick look shows that the contact us link is not actually an email address, but an 'email form' much like the email forms to send emails between users on the forums. And is most likely hard coded into the forum system.
For the email issue. The fact that it worked, then stopped, appears to point towards a problem at gmails end. It may not be. Right now, we don't have the resources to work on this problem, which, when compared to other jobs that need doing, is fairly minor.
There is a possibility with the password problem though. When you change your email address on the forums, you have to enter your old password. On the same page is the password change area. It's possible that your browser has auto-filled this with your username.
As I said before, this isn't really high on the priorities list at the moment. I'll keep thinking about it, and I'll throw thoughts at Mike. But at this stage the only suggestion I can make is for you to keep fiddling.
Zec