If you install the Host IPS product without using Altiris (use the manual install method as described in the Host IPS Install Guide; extract zip package to the local system and run McAfeeHIP_ClientSetup.exe), do you still have the same problem?
It is not related to Altiris. It is somewhere related to the rights when installing and the fact that we still use the windows FW activated and the HIPS FW disabled.
It can be easily simulated with a psexec command (running with system priveledges) . After the reboot the system doesn't get an IP and logging on is impossible.
Also the distribution via EPo is not installing correctly whe the windows 7 FW is active.