I followed the docs at Heroku and Zerigo to set up a custom domain for MYAPP.heroku.com. When I navigate to myapp.heroku.com, everything works fine. But when I navigate to myapp.com or www.myapp.com, I get the error "Heroku | No such app"
host myapp.heroku.com
myapp.heroku.com is an alias for proxy.heroku.com.
[.....]
looks good, and
host www.myapp.com
www.myapp.com is an alias for proxy.heroku.com.
[.....]
looks good too. But I still get "Heroku | No such app".
totally baffled at this point
The DNS entries look fine - provided you've added www.myapp.com as a custom domain to your application on Heroku then it should work fine. You can check this by viewing the application from the 'My Apps' tab on heroku.com and making sure the custom domain is listed in the domains section as 'www.myapp.com'.
If thats there then I'd log a ticket with support as you're doing everything right.
UPDATE: Heroku Status was just updated with a problem surrounding custom domains, it's likely that this is your problem - https://status.heroku.com/
HEROKU UPDATE: Engineers are still investigating the source of issues regarding custom domains. We have determined that only domains added or updated in the past 48 hours should be affected. We'll continue to provide more information as it becomes available.