Router gets confused

Twice today my mail router has had problems delivering mail. When it malfunctions, I get the following:

03/15/2003 07:34:49 PM Router: Unable to deliver message 000E2C84 to person@abc.com

03/15/2003 07:34:49 PM Recipient user name person@abc.com not unique. Several matches found in Domino Directory.

After I restart the router, the mail is delivered to person@abc.com properly.

What is causing this? How can it be fixed?

Thanks for any help.

Subject: Router gets confused

Try to do Ctrl-Shift-F9 on your Domino directory. The view index might be corrupted.