Lets Rule out network permissions on these machines.
You can export a package from SEPM. Copy that package to the client machines manually and double click on it to initiate the installation as an administrative user.
I am not suggesting this as a solution, but just to isolate the issue. If you are able to install the SEP client locally, then there are lack of network permissions thats stopping the installation.
However, if you have the same issue installing the package locally, then you an attach the SEP_INST.log to your post.
So that we can take a look at it. Also, since we are troubleshooting installation, lets choose the installation method as unattanded instead of silent.
If the installation rolls back, please try to notice the action being performed by the installer [ e.g. validating installation, installing liveupdate..etc]
Let me know if you need more clarification.
Cheers,
Aniket Amdekar