Enumerating UserProfiles

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What is the preferred method for enumerating UserProfiles to anonymous users
in MOSS 2007?

We are trying to build a staff directory, based off custom properties
imported by the SSP. We have a custom web part which does a great job, but it
does not work for anonymous users.

We are currently using UserProfileManager.GetUserProfile(), but we get the
error:

"The user could not be authenticated to the Web site being accessed."

Any help would be greatly appreciated...
.