[Zope] Unable to login to zope management interface on Ubuntu

Hi, I'm running Ubuntu (warty). I just installed zope 2.6.4-1.1 through synaptic. I created a user with the "zpasswd inituser" command. I could connect to the zope server on port 9673. The zope quick start page comes up. When I click on the management interface link, I'm asked to enter the username and password. Even after I enter it correctly (the same values that I entered through zpasswd), I keep getting the same dialog box over and over again and I'm not able to proceed beyond this stage. Where am I going wrong? Vishwas.