I recently made a new installation of dotnetnuke that started without a problem.  I logged in succesfully and added some pages, etc. and everything functioned as usual (this is my sixth installation).  Eventually after a period of inactivity, my session timed out and I attempted to login again as host.  At this point I received an error that my password was incorrect.  I know this is not the case because the password was cut and pasted from its original source.  The same was the case for the admin password.  I attempted to have the password emailed because that seemed to be the next logical step and I received an error that the password could not be emailed.  Does anyone have any next steps for troubleshooting this problem?

I have seen this happen if for some reason the InstallationDate node is not in the web.config and you get an app restart, which cause it to change your machine keys.

What happens is people will upgrade and move over their custom information to the new web.config, but miss the InstallationDate node (which is easy to do).

So long story short, check your machine key against a backup, and make sure the InstallationDate node is in your web.config.

Yes, that would correct the problem for host, and since it is a fresh install I am assuming you do not have other users with passwords stored using different machine keys.