Enterprise Manage rkeeps trying to log servers in

I have a user that has several of our SQL server registered in Enterprise
Manager. When I go into the servers Event Viewer, I see the persons login
continuosly failing . The odd thing is that he has the servers registered to
use the sa account, and prompt to login, but the logins I am seeing in the
event viewer are trying to use his workstation login name and not sa. I have
not seen this issue with any other user. This is happening with every server
he has registered in Enterprise Manager, and as soon as he removes a server
from it, I stop seeing the failed login attempts. Any idea what would be
causing this?