将用户添加为网站所有者时出现SharePoint错误

I have a MOSS 2007 site which I'm an admin for. In the 'People and Groups' area for a site, I'm trying to add a user as a site owner. On the 'Add User' page, I add the name of the user and click 'OK', after which I get this totally useless error:I have a MOSS 2007 site which I'm an admin for.