iNotes address window problem

Using the standard iNotes template (either inotes5 or inotes60), users connect to our Domino server. They are running Windows 2000 Professional SP2 and Internet Explorer 5.5 SP1. When you compose a new Memo and click the To: link to bring up the address book, the new address book window pops up, but it is completely grey and blank. This works fine on our non-back office machines, I’ve tried this against 5.0.9 and 6.0.1 Domino Servers. We are using Microsoft’s Web Browser Interface instead of the standard out of the box Internet Explorer. Our main question is what is iNotes doing when you click the To: link? Is it doing a javascript window command or something else. Has anyone else seen this behavior?