I tried researching this, but couldn't find a solution as of yet.

I moved DNN from one production server to another and now no users/admins can login to the DNN installation.  This affecting DNN 2.x, 3.x and 4.x sites.  I believe it is an issue with the machinevalidationkey and machinedecryptionkey being different between servers.  I have already fixed the admin/host accounts with a post I found,  but am not sure how to fix the issue so that I don't have to reset all the users passwords.

josh a good idea when migrating would be to run a merge application on you old web.config and your new one.
I just went through a similar process on a major installation we have running and this was one of the first issues I encountered.

Nice to see you around, Josh... welcome back ;)

For some who may not realize... Josh is the "Alex Shirley" of versions 1.x and 2.x!

Josh, it sounds like you are merging one set of files with another database?  If I read that correctly, this means that you need to be using the keys from the OLD web.config file... not the new one you are copying in.  The purpose of these keys is to enable encryption and decryption of data that is ultimately stored in the DB.  By changing that in web.config (to the newer one), you render all the old passwords inoperable because they will not be decrypted properly.  Similarly... any NEW ones will appear to work, but once you reapply the OLD key, they will be rendered inoperable because the old key won't decrypt them properly.  You need to resolve this as quickly as possible to avoid additional data loss.  Encryption/Decryption keys, once set (in web.config) should never be changed.

Cheers

Scott Willhite, Co-Founder DNN