False error: Could not find this user account (kinda urgent)

Hi-

I keep getting the error "Could not find this user account" when trying to update a user. I added the user id and username to the error message to ensure that they were available, and they show up just fine in the error message. Obviously the user exists or else the login would not work, so I am not sure what is causing the error. Any ideas?

BTW: I have Debug on for this form and am not getting any debugging information for any of the read or save actions.