Hello Ian,
I'm currently running the most recent version of DNN (as of 1 month ago), and I'm experiencing the same issue. I have only logged on with the Administrator Account. I tried using the Host account for the 1st time, using the username/password combo you suggested, to no avail. I have looked everywhere for documentation. My next resort will be to look at the database tables. I'm using Sql Server 2005 Enterprise Edition. IIS 6.0 and Windows 2000.
Can I re-add the host account. I tried the password reminder feature, but it says that the account does not exist.
This whole thing came up, because I am trying to setup SMTP mail. Thanks for any assistance you can provide.
-Joe