I have set up multiple mysql databases about 3 hours ago. They apear on the MySql tab of the admin page, but are not accessable via SSH or by dbhost.mydomain.net (dns error).
Are the DB's set up manually? This would explain why they're not up yet
No, they are not set up manually. Seems like for some reason DNS is taking longer to propigate across the dreamhost system than usual over the past few days. Give it an other hour, and if it's not working by them contact support.