Hello All,
  I just upgraded one of my servers from 4.3.4 to 4.4.1 and everytime I try and log in it gives me:
A critical error has occurred.
Object reference not set to an instance of an object.

and doesn't actually log me in...Has anyone run into this?

Thanks!

I've got a similar problem, except worse.  EVERY single time I try to upgrade ANY DNN site from 4.3.x to 4.4.1 The whole entire site breaks and just says "Critical Error Occurred".  I've been trying to do this several times, and always fails.  I've been with DotNetNuke a loooooong time and this is the first time that I've had this much problems upgrading sites...  I'm going to have to kill the site and start over.  I've even tried putting the "Missing Assemblies" out there, but no luck....

Ok, tried a couple things with the upgrade but still no luck.

-Thought is might have something to do with first upgrading the original server (LIVE), so I tried upgrading a test site on that machine, still get the error when trying to log in with an existing account.

-Thought it might have something to do with upgrading from 4.3.4 to 4.4.1, so I had a copy of the upgrade to 4.3.5 and tried that.  Still get the error.

I know it has something to do with the ValidationKey/DecryptionKey, cause we can create new accounts and log in fine with those after the upgrades.  But I am coping exactly what I had before in the web.config file.  Also added the "InstallationDate" under the appsettings section thinking it might need that also.  Still no luck.

Please, can anyone think of anything that I didn't do or something that is causing the login error after upgrade?  I have the site that I am trying to upgrade in version control, so I can rollback and try any suggestions.

Thanks!!!