I have a proxy setup:
Zabbix proxy v2.0.6 (revision 35158) (22 April 2013)
Compilation time: Jul 30 2013 15:25:04
Server:
Zabbix server v2.0.6 (revision 35158) (22 April 2013)
Compilation time: May 7 2013 14:58:16
I add the hosts to the proxy via Administration -> DM

About 5-10 Minutes later they drop out

looking at the logs from the proxy. Nothing in the server log.
6950:20130903:153206.945 cannot send list of active checks to [xx.xx.xx]: host [oit-wcl-tapp-06.sea.oit.unlv.edu] not found
6950:20130903:153214.764 cannot send list of active checks to [xx.xx.xx.xx]: host [oit-wcl-tapp-03.sea.oit.unlv.edu] not found
Zabbix proxy v2.0.6 (revision 35158) (22 April 2013)
Compilation time: Jul 30 2013 15:25:04
Server:
Zabbix server v2.0.6 (revision 35158) (22 April 2013)
Compilation time: May 7 2013 14:58:16
I add the hosts to the proxy via Administration -> DM

About 5-10 Minutes later they drop out

looking at the logs from the proxy. Nothing in the server log.
6950:20130903:153206.945 cannot send list of active checks to [xx.xx.xx]: host [oit-wcl-tapp-06.sea.oit.unlv.edu] not found
6950:20130903:153214.764 cannot send list of active checks to [xx.xx.xx.xx]: host [oit-wcl-tapp-03.sea.oit.unlv.edu] not found