First, I would verify that basic networking is right between the 2 lan's... ping, tracert, etc... all looks good ?
Firewall on the clients stopping any traffic ?
Can you manually install the agent from the suspect subnets?
If so, start the epo agent monitor (cmdagent.exe /s) and see if it communicates properly.
fwiw - you have 2 totally separate epo servers, 1 for each subnet ? that seems like 2x the maintenance, maybe running it on undersized hardware....fun stuff.