PeoplePicker apparently sees the same userid as two people

In short, my suspicion is that SharePoint has the same userid credentials in its metadata twice, with the result being that the permissions on the site for this userid gets messed up (that is, the userid cannot log in to the site).

I did get an error message one time to the effect "myuser" resolves to multiple names... 

Also, after I hit find in the PeoplePicker, and then hit Add, two users get put in the Add box, both with the same name.

In short, anyone ever heard of something to the effect a user, who may have been deleted in the domain and re-added, somehow is registered twice within SharePoint's security?  Any suggestions / comments appreciated.