Hi, I managed to upgrade one of the sites we host last night from 4.0.2 to 4.4.1. The site appears fine to the average visitor, but when I click the login button, I get "A critical error has occurred. Value cannot be null. Parameter name: format" at the top of the content pane on whatever page I am on when I click it. I can't find any instances of someone having the same problem by searching the web or these forums. I'm wondering if anyone can make a suggestion. You can view the error at http://www.highriver.ca then click login near the top-right. Thanks for any help you can provide.

It seems the upgrade process isn't very waterproof.
We've tried to upgrade several DNN install's as well and came across strange errors too.
Most of the errors seem to be related to the users / security system of DNN.

Recently we did a 4.3.7 to a 4.4.1 and everything seemed to work fine, except when we logged in as a host, we could see 'host' as a menu item, but we could not expand the host menu.
So DNN sees that it must be a host, but on another level does not allow any host specific actions.

Did you check web.config?
- change the minRequiredPassWordLength to a smaller value
- change the ApplicationName to the name of the server, or to ""

Similar problem.  I upgraded from 4.3.7 but can't log in.  None of the host or admin passwords work.  Not even the defaults.  I get a critical error and can't access and admin menus.  Has anyone found a solution to the upgrade problem?  Last time I had to start fresh and it took me days to recover all my addtional module and the data stored with them.

I did notice that if I register a new user I can gain access to registered user area, but still no admin functions.

Peter