The status shown in the push report page isn't always reliable. In most cases, the install was actually successful. Is it stuck at Starting Download or Starting Install?
Do you have additional details on the discovery type you're running, and what the exact status is?
Regarding site servers, it can take some time for them to appear, as it requires basic inventory and a delta resource membership update to occur. They must also be valid as site servers and have the Symantec Management Agent installed.
If you visit a computer that you tried to push to, have you verified that the agent really wasn't installed? The account used for the push should have administrator rights on the computer being pushed to.
I'd also review these KB's:
http://www.symantec.com/docs/TECH11685
http://www.symantec.com/docs/TECH13407
Do you have any relevant errors in the Altiris Log Viewer on the NS?
I would recommend moving the Workflow/ServiceDesk portion of this question to the Workflow or ServiceDesk forums. Probably won't get an overwhelming response in this forum.