First thing's first.
Do the computers have a firewall enabled?
Are the computers windows Vista, or XP?
XP seems to work ok with the firewalls turned off.
vista has been known in my networks to not like to accept the package (mostly due to their firewall).
The first thing is first, check your remote installation log from within the ADNM console. I can't remember exactly where it is, but if you look in the menu, I think it's under View > AMS Logs > Remote Installation log or something like that. If you're a Network Admin, you should be able to figure it out.
Next, find out if it's permissions that are blocking you or what.
I've found that I've either had to disable all local firewalls, or add the appropriate entries into the firewalls using group policy if remote installation fails.
If you need help, I can give you the exact lines that you are supposed to put in your group policy to enable the ports on your clients, for proper installation.