I was getting similar error in some machines when trying to install the agent manually . What I did to solve the problem was this. (found here https://www-secure.symantec.com/connect/blogs/uninstalling-altiris-agents)
Use the AeXAgentUtil.exe located at C:\Program Files\Altiris\Altiris Agent\AeXAgentUtil.exe
I run the following commands
AeXAgentUtil.exe /DeleteDevices - Deletes known Altiris legacy device drivers.
AeXAgentUtil.exe /UninstallAgents - Deletes all registered agents.
AeXAgentUtil.exe /Clean - Attempts to completely remove the Agent. It will attempt to detect the relevant version and remove all files and registry entries.
Then I deleted Altiris registry entry at HKEY_LOCAL_MACHINE -> SOFTWARE -> Altiris
Also I noticed some problems with machines where the command line bellow was used to install the agent.
aexnsc.exe –s –a ns=”server.altiris.com” nsweb=”http://server.altiris.com/Altiris” /s
instead of this
aexnsc.exe /install /ns=server.altiris.com /nsweb=”http://server.altiris.com/Altiris”
or aexnsc.exe /install /ns=server.altiris.com ( I used this to install the agent again without errors)
sorry about my english