When trying to set up an Alpha 6 test I was having problems adding hosts. I would add a host, but it would seem to dissapear from the display. I found that refreshing the display would bring it back. It seems that a number of the pages were being served from the browser cache. I circumvented the problem by setting the Apache cache default for the ZABBIX site to be 1 second. This works for me for testing a small site, but might be less than optimal for a large installation.