Iis app pool set credentials not working for specific network account

I am trying to set app pool credentials for a speccific domain account for an ASP.net MVC project on iis 7.5 on a Windows 7 enterprise server. I am using .Net version 4 and I believe this is set correctly throughout the iis interface.

We have set up a user account in the form of domainName\username with a specific password, that I'll denote password0 (not its real name). When I enter the user name (domainName\username) and the specific password (password0) and confirm it, the Set Credentials gives a message box saying The specified password is invalid. Type a new password.

After much research on Stack Overflow and elsewhere, this almost always is not a password problem (note how well the particular error message was chosen, but I digress), and usually a configuration problem with the account and the settings of the machine.

One site recommended as a work around to use command prompt to enter the settings, which does work for the app pool — for those interested, the format is:

appcmd set config /section:applicationPools "/[name='specificAppPoolName'].processModel.identityType:SpecificUser" "/[name='specificAppPoolName'].processModel.userName:domainName\username" "/[name='specificAppPoolName'].processModel.password:password0"

This works, however, for the next step, when I go to the iis site using the app pool, and use
iis –> Site –> specific site –> Basic Settings

and try to use the "Connect as" button, neither the passthrough nor the specific user works, if I try to set the specific user, the old password problem re-appears (undoubtedly it is not a mis-typed password, thanks again to whoever sets these error messages).

Test settings gives things like Login failure: unknown user name or bad password with code 0x8007052E (authentication)
and the credentials used to access the specified physical path are invalid (authorization)

NOTE: I have already run

aspnet_regiis -ga domainName\username 

several times.

I have also specifically added domainName\username to the published folder for the MVC app.

I realize there are related stack overflow posts but I haven't been able to get anything to work and I am reluctant to re-open old questions. This is a fairly important set-up to make MVC generally a workable solution in our shop.

I have added some of the things that I tried in the comments, however, while some of the things "work" in the sense of being valid operations, to date they have not fixed the over-all problem.

Does anyone know how to do this, a work-around, or perhaps even have a link to a step-by-step set up for this configuration scenario?

Thanks in advance!