Windows 7 Pro clearing cached credentials to force re-authentication

The situation:

Using windows explorer to access a shared network resource, for example, \\blah\folder\folder2 - the first time I try this on a new installation, it requires authentication (user/pass) which I provide (this is on a workgroup, not a domain). That's fine.

The goal:

I want a way to force Windows 7 Pro to forget the authentication and ask for a new authentication next time an access is attempted for that share.

Here's what I have tried, and what has not worked:

Windows Explorer -> Tools -> Disconnect Network Drive (it doesn't work because there is no mapped network drive to disconnect; next connection attempt does not ask for authentication)

From command prompt (run As administrator): rundll32.exe keymgr.dll, KRShowKeyMgr -- Then select any network share to clear credentials for, then click delete button. (no network shares listed; next connection attempt does not ask for authentication)

From command prompt (run As administrator): net use * /delete /yes
(nothing happens; next connection attempt does not ask for authentication)

From command prompt (run As administrator): control userpasswords2
Go to advanced tab, click on manage passwords. This brings up the credential manager (can also get to credential manager directly from control panel). Find credentials to delete (windows, certificate-based, or generic) - there are currently none listed, though there had been earlier, and all were deleted. No change; next connection attempt does not ask for authentication.

From command prompt (run As administrator): secpol.msc
Go to security settings -> local policies -> security options -> Network access: Do not allow storage of passwords and credentials for network authentication.
Enable it. Exit and reboot. No change; next connection attempt does not ask for authentication.

I have tried all of these with or without rebooting immediately after. No luck.
I'm open to suggestion.

Ilya