Outlook 2010 client calendar displaying /O= /OU=

I have an Outlook 2010 end user who suddenly in his calendar when he creates a new entry, rather than showing his Display Name as it should, it shows /O=COMPANY NAME/OU=OU/etc, etc.

This just started recently, he's been on Outlook 2010 for over  a year now. His mailbox hasn't changed databases, none of the common culprits I can think of. Has anyone else run into this and found a solution?

Thanks!