NOT MUCH to go on....
Can you launch it from a workstation (or another server)?
What is the difference between those machines, and your ePO server, internet-wise? (Proxy/hostfile/dns/IE/Chrome/Firefox)
evasherley Did you check Orion.log???
before that you may need to enable debugging if not enabled, using below process
Find Log-config.xml file under Pro file\McAfee\ePO\server\Conf\orion
Openn file and at the bottom you will find "priority value=warn" change warn to debug and save.
restart tomcat service, and ePO application service and try login.
Check for the error logs.
Hope this help you to find issue.