[otrs] Users cannot select a customer using Customer User Management

I noticed a weird issue in OTRS. When signed in as someone with RW Admin rights, I am able to click the "Customer" link next to Options and pick a customer using the Customer User Management window. However, when signed in as a user the window comes up with "Internet Explorer cannot display the webpage". This seems to be a permissions issue, but I cannot figure out where that parameter is, even after looking all through SysConfig and trying to grant all permissions shy of "RW" for admin. Does anyone have any ideas? -Raymond